feat(snapshots): AE scene-snapshot pipeline + admin trigger (Epic C, C1)

Per-scene preview thumbnails for templates. Admin clicks "ساخت پیش‌نمایش
صحنه‌ها" → one single-frame AE render per scene → content.scenes.snapshot_url
→ shown as a thumbnail in the admin scene list (and available to the studio).

- migration 30_render_snapshot_jobs.sql: render.snapshot_jobs (queued|running|
  done|error, per scene, image_url).
- render-svc: db/snapshotjobs.go (EnqueueSceneSnapshots, List, Claim, SetResult
  -> writes content.scenes.snapshot_url cross-schema, SetError); handlers/
  snapshotjobs.go (admin POST/GET /v1/scene-snapshots/:project_id + node-facing
  internal claim/result/fail); main.go routes; gateway route.
- devworker: RunSnapshots — fulfils snapshot jobs with a generated placeholder
  PNG (data: URL, scene-key-tinted) so the flow is verifiable without an AE node.
  Gated by RENDER_DEV_SNAPSHOTS (default off; never hijacks real render jobs).
- admin UI: ProjectScenes "generate snapshots" button (enqueue + poll + reload)
  and a thumbnail (snapshot_url || image) per scene row.

Verified e2e via the dev mock: enqueue -> jobs run -> content.scenes.snapshot_url
populated -> scenes API returns it -> admin renders the thumbnail.

Remaining (C2): node-agent real-AE runner — claim snapshot, aerender -s0 -e0 ->
ffmpeg still -> upload to a PERMANENT URL (mirror file-svc, not the time-limited
export presign) -> post result. Needs a live AE node to build + verify.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/gateway/cmd/server/main.go

@@ -141,6 +141,7 @@ func main() {
 	v1.Any("/admin-exports/*path", apiRL,  auth, render.Handler())
 	v1.Any("/admin-renders",      apiRL,   auth, render.Handler())
 	v1.Any("/template-bundles/*path", apiRL, auth, render.Handler())
+	v1.Any("/scene-snapshots/*path", apiRL, auth, render.Handler())
 	v1.Any("/template-scans/*path", apiRL, auth, render.Handler())
 	v1.Any("/template-scan-jobs/*path", apiRL, auth, render.Handler())
 	v1.Any("/node-updates/*path", apiRL,   auth, render.Handler())

services/render/cmd/server/main.go

@@ -82,6 +82,7 @@ func main() {
 	fontH    := handlers.NewFontHandler(store)
 	bundleH  := handlers.NewTemplateBundleHandler(mc, minioTemplatesBucket)
 	scanH    := handlers.NewScanHandler(store, mc, minioTemplatesBucket)
+	snapJobH := handlers.NewSnapshotJobHandler(store, mc, minioTemplatesBucket)
 	internalH := handlers.NewInternalHandler(store, notifyClient, mc, minioTemplatesBucket, minioBucket)
 
 	// ── Dev mock worker (no AE node needed) ────────────────────────────────────
@@ -90,6 +91,11 @@ func main() {
 	if devWorker {
 		go devworker.New(store).Run(context.Background())
 	}
+	// Snapshot-only dev mock: fulfils scene-snapshot jobs with a generated
+	// placeholder (no AE), gated separately so it never hijacks real render jobs.
+	if getEnv("RENDER_DEV_SNAPSHOTS", "false") == "true" {
+		go devworker.New(store).RunSnapshots(context.Background())
+	}
 
 	// ── Router ────────────────────────────────────────────────────────────────
 	r := gin.Default()
@@ -174,6 +180,10 @@ func main() {
 	v1.POST("/template-bundles/:project_id", auth, admin, bundleH.Set)
 
 	// ── Template scans (admin: read scenes/colours/configs from the AEP) ───────
+	// ── Scene snapshots (admin: render one frame per scene from AE) ────────────
+	v1.POST("/scene-snapshots/:project_id", auth, admin, snapJobH.Enqueue)
+	v1.GET("/scene-snapshots/:project_id", auth, admin, snapJobH.List)
+
 	v1.POST("/template-scans/:project_id/quick", auth, admin, scanH.QuickScan) // headless Go quick-scan
 	v1.POST("/template-scans/:project_id/jobs", auth, admin, scanH.CreateJob)  // queue an AE full scan
 	v1.GET("/template-scan-jobs/:id", auth, admin, scanH.GetJob)
@@ -205,6 +215,11 @@ func main() {
 		internal.POST("/render/jobs/:job_id/crash", internalH.Crash)
 		internal.POST("/render/jobs/:job_id/replica-ready", internalH.ReplicaReady)
 
+		// AE scene snapshots (node claims, renders one frame, posts the image URL)
+		internal.POST("/snapshot/claim", snapJobH.Claim)
+		internal.POST("/snapshot/:id/result", snapJobH.Result)
+		internal.POST("/snapshot/:id/fail", snapJobH.Fail)
+
 		// AE scan jobs (node claims, runs scan.jsx, posts the ScanResult back)
 		internal.POST("/scan/claim", scanH.Claim)
 		internal.GET("/scan/:id/status", scanH.Status) // node watchdog (cancel detection)

services/render/internal/db/snapshotjobs.go

@@ -0,0 +1,125 @@
+package db
+
+import (
+	"context"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+)
+
+// SnapshotJob is an async "render one frame of a scene" job (status row).
+type SnapshotJob struct {
+	ID       uuid.UUID `json:"id"`
+	SceneID  uuid.UUID `json:"scene_id"`
+	SceneKey string    `json:"scene_key"`
+	Status   string    `json:"status"` // queued | running | done | error
+	ImageURL *string   `json:"image_url,omitempty"`
+	Error    *string   `json:"error,omitempty"`
+}
+
+// SnapshotClaim is the minimal info a node needs to render a claimed snapshot.
+type SnapshotClaim struct {
+	ID        uuid.UUID
+	ProjectID uuid.UUID
+	SceneID   uuid.UUID
+	SceneKey  string
+	CompName  string
+	Frame     int
+}
+
+// EnqueueSceneSnapshots clears any prior snapshot jobs for the project and queues
+// one fresh job per active scene (comp_name defaults to the scene key — a comp of
+// that name; the node falls back to the render comp when it does not exist).
+// Returns the number of jobs queued.
+func (s *Store) EnqueueSceneSnapshots(ctx context.Context, projectID uuid.UUID) (int, error) {
+	tx, err := s.pool.Begin(ctx)
+	if err != nil {
+		return 0, err
+	}
+	defer tx.Rollback(ctx)
+
+	if _, err = tx.Exec(ctx, `DELETE FROM render.snapshot_jobs WHERE project_id = $1`, projectID); err != nil {
+		return 0, err
+	}
+	tag, err := tx.Exec(ctx, `
+		INSERT INTO render.snapshot_jobs (project_id, scene_id, scene_key, comp_name, frame, status)
+		SELECT $1, sc.id, sc.key, sc.key, 0, 'queued'
+		FROM content.scenes sc
+		WHERE sc.project_id = $1 AND sc.deleted_at IS NULL AND sc.is_active = true`, projectID)
+	if err != nil {
+		return 0, err
+	}
+	if err = tx.Commit(ctx); err != nil {
+		return 0, err
+	}
+	return int(tag.RowsAffected()), nil
+}
+
+// ListSnapshotJobs returns the snapshot jobs for a project (for polling).
+func (s *Store) ListSnapshotJobs(ctx context.Context, projectID uuid.UUID) ([]SnapshotJob, error) {
+	rows, err := s.pool.Query(ctx,
+		`SELECT id, scene_id, scene_key, status, image_url, error
+		 FROM render.snapshot_jobs WHERE project_id = $1 ORDER BY created_at`, projectID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []SnapshotJob
+	for rows.Next() {
+		var j SnapshotJob
+		if err := rows.Scan(&j.ID, &j.SceneID, &j.SceneKey, &j.Status, &j.ImageURL, &j.Error); err != nil {
+			return nil, err
+		}
+		out = append(out, j)
+	}
+	return out, rows.Err()
+}
+
+// ClaimSnapshotJob atomically grabs the oldest queued snapshot for a node.
+// Returns nil when the queue is empty.
+func (s *Store) ClaimSnapshotJob(ctx context.Context, nodeID uuid.UUID) (*SnapshotClaim, error) {
+	var c SnapshotClaim
+	err := s.pool.QueryRow(ctx, `
+		UPDATE render.snapshot_jobs SET status = 'running', node_id = $1, updated_at = NOW()
+		WHERE id = (
+			SELECT id FROM render.snapshot_jobs
+			WHERE status = 'queued'
+			ORDER BY created_at
+			LIMIT 1 FOR UPDATE SKIP LOCKED
+		)
+		RETURNING id, project_id, scene_id, scene_key, comp_name, frame`,
+		nodeID).Scan(&c.ID, &c.ProjectID, &c.SceneID, &c.SceneKey, &c.CompName, &c.Frame)
+	if err != nil {
+		if err == pgx.ErrNoRows {
+			return nil, nil
+		}
+		return nil, err
+	}
+	return &c, nil
+}
+
+// SetSnapshotResult marks a running snapshot done with its image URL and writes
+// that URL onto the content scene (same DB, cross-schema) so the studio + admin
+// render a real thumbnail.
+func (s *Store) SetSnapshotResult(ctx context.Context, id uuid.UUID, imageURL string) error {
+	var sceneID uuid.UUID
+	err := s.pool.QueryRow(ctx,
+		`UPDATE render.snapshot_jobs SET status = 'done', image_url = $2, error = NULL, updated_at = NOW()
+		 WHERE id = $1 AND status = 'running' RETURNING scene_id`, id, imageURL).Scan(&sceneID)
+	if err != nil {
+		if err == pgx.ErrNoRows {
+			return nil // job no longer running (cancelled/regenerated) — ignore late result
+		}
+		return err
+	}
+	_, err = s.pool.Exec(ctx,
+		`UPDATE content.scenes SET snapshot_url = $2, updated_at = NOW() WHERE id = $1`, sceneID, imageURL)
+	return err
+}
+
+func (s *Store) SetSnapshotError(ctx context.Context, id uuid.UUID, msg string) error {
+	_, err := s.pool.Exec(ctx,
+		`UPDATE render.snapshot_jobs SET status = 'error', error = $2, updated_at = NOW() WHERE id = $1 AND status = 'running'`,
+		id, msg)
+	return err
+}

services/render/internal/devworker/devworker.go

@@ -102,6 +102,62 @@ func (w *Worker) simulate(ctx context.Context, jobID uuid.UUID) {
 	log.Printf("[devworker] job %s done", jobID)
 }
 
+// ── Snapshot mock ─────────────────────────────────────────────────────────────
+// devSnapshotNode is the synthetic node id the mock records on claimed snapshots.
+var devSnapshotNode = uuid.MustParse("00000000-0000-0000-0000-0000000000aa")
+
+// RunSnapshots fulfils queued scene-snapshot jobs with a generated placeholder
+// image (no AE) so the snapshot flow is exercisable in development. Gated by its
+// own flag so it never touches real render jobs. Production uses real nodes.
+func (w *Worker) RunSnapshots(ctx context.Context) {
+	log.Printf("[devworker] snapshot mock started (poll %s) — NOT for production", w.interval)
+	ticker := time.NewTicker(w.interval)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			w.snapTick(ctx)
+		}
+	}
+}
+
+func (w *Worker) snapTick(ctx context.Context) {
+	claim, err := w.store.ClaimSnapshotJob(ctx, devSnapshotNode)
+	if err != nil {
+		log.Printf("[devworker] snapshot claim error: %v", err)
+		return
+	}
+	if claim == nil {
+		return // queue empty
+	}
+	if err := w.store.SetSnapshotResult(ctx, claim.ID, snapshotPlaceholder(claim.SceneKey)); err != nil {
+		log.Printf("[devworker] snapshot %s result failed: %v", claim.ID, err)
+		_ = w.store.SetSnapshotError(ctx, claim.ID, err.Error())
+		return
+	}
+	log.Printf("[devworker] snapshot %s (scene %s) done", claim.ID, claim.SceneKey)
+}
+
+// snapshotPlaceholder builds a 480×270 PNG card tinted by the scene key with a
+// little "play" block, returned as a data: URL so the dev path needs no storage.
+func snapshotPlaceholder(sceneKey string) string {
+	const w, h = 480, 270
+	var sum uint32
+	for _, r := range sceneKey {
+		sum = sum*31 + uint32(r)
+	}
+	base := color.RGBA{uint8(40 + sum%120), uint8(40 + (sum/120)%120), uint8(80 + (sum/7)%150), 255}
+	img := image.NewRGBA(image.Rect(0, 0, w, h))
+	draw.Draw(img, img.Bounds(), &image.Uniform{base}, image.Point{}, draw.Src)
+	draw.Draw(img, image.Rect(0, h/2-30, w, h/2+30), &image.Uniform{color.RGBA{0, 0, 0, 60}}, image.Point{}, draw.Over)
+	draw.Draw(img, image.Rect(w/2-18, h/2-18, w/2+18, h/2+18), &image.Uniform{color.RGBA{255, 255, 255, 230}}, image.Point{}, draw.Over)
+	var buf bytes.Buffer
+	_ = png.Encode(&buf, img)
+	return "data:image/png;base64," + base64.StdEncoding.EncodeToString(buf.Bytes())
+}
+
 // previewB64 builds a 320×180 PNG with a progress bar — same idea as the node
 // agent's GeneratePreviewB64, kept local so render-svc has no node-agent dep.
 func previewB64(pct int) string {

services/render/internal/handlers/snapshotjobs.go

@@ -0,0 +1,133 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/flatrender/render-svc/internal/db"
+	"github.com/flatrender/render-svc/internal/models"
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"github.com/minio/minio-go/v7"
+)
+
+// SnapshotJobHandler queues per-scene single-frame AE snapshot jobs and exposes
+// the node-facing claim/result/fail lifecycle. On result it writes the image URL
+// onto content.scenes.snapshot_url (in the store, cross-schema).
+type SnapshotJobHandler struct {
+	store           *db.Store
+	minio           *minio.Client
+	templatesBucket string
+}
+
+func NewSnapshotJobHandler(store *db.Store, mc *minio.Client, templatesBucket string) *SnapshotJobHandler {
+	return &SnapshotJobHandler{store: store, minio: mc, templatesBucket: templatesBucket}
+}
+
+// POST /v1/scene-snapshots/:project_id  (admin) → queue one job per active scene.
+func (h *SnapshotJobHandler) Enqueue(c *gin.Context) {
+	pid, err := uuid.Parse(c.Param("project_id"))
+	if err != nil {
+		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid project_id"})
+		return
+	}
+	n, err := h.store.EnqueueSceneSnapshots(c.Request.Context(), pid)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, models.APIError{Code: "internal_error", Message: err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"enqueued": n})
+}
+
+// GET /v1/scene-snapshots/:project_id  (admin) → job statuses for polling.
+func (h *SnapshotJobHandler) List(c *gin.Context) {
+	pid, err := uuid.Parse(c.Param("project_id"))
+	if err != nil {
+		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid project_id"})
+		return
+	}
+	jobs, err := h.store.ListSnapshotJobs(c.Request.Context(), pid)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, models.APIError{Code: "internal_error", Message: err.Error()})
+		return
+	}
+	if jobs == nil {
+		jobs = []db.SnapshotJob{}
+	}
+	c.JSON(http.StatusOK, gin.H{"jobs": jobs})
+}
+
+// POST /v1/internal/snapshot/claim  (node, HMAC)
+func (h *SnapshotJobHandler) Claim(c *gin.Context) {
+	var req models.ClaimJobRequest
+	_ = c.ShouldBindJSON(&req)
+
+	claim, err := h.store.ClaimSnapshotJob(c.Request.Context(), req.NodeID)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, models.APIError{Code: "internal_error", Message: err.Error()})
+		return
+	}
+	if claim == nil {
+		c.Status(http.StatusNoContent)
+		return
+	}
+	url, isBundle, md5 := resolveTemplateObject(h.minio, h.templatesBucket, claim.ProjectID)
+	if url == "" {
+		_ = h.store.SetSnapshotError(c.Request.Context(), claim.ID,
+			"no template stored for this project — upload the .aep from «فایل‌ها» first")
+		c.Status(http.StatusNoContent)
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{
+		"snapshot_job_id":  claim.ID,
+		"project_id":       claim.ProjectID,
+		"scene_id":         claim.SceneID,
+		"scene_key":        claim.SceneKey,
+		"comp_name":        claim.CompName,
+		"frame":            claim.Frame,
+		"aep_download_url": url,
+		"is_bundle":        isBundle,
+		"bundle_md5":       md5,
+	})
+}
+
+// POST /v1/internal/snapshot/:id/result  (node, HMAC)  body {image_url}
+func (h *SnapshotJobHandler) Result(c *gin.Context) {
+	id, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid id"})
+		return
+	}
+	var req struct {
+		ImageURL string `json:"image_url"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil || req.ImageURL == "" {
+		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "image_url required"})
+		return
+	}
+	if err := h.store.SetSnapshotResult(c.Request.Context(), id, req.ImageURL); err != nil {
+		c.JSON(http.StatusInternalServerError, models.APIError{Code: "internal_error", Message: err.Error()})
+		return
+	}
+	c.Status(http.StatusNoContent)
+}
+
+// POST /v1/internal/snapshot/:id/fail  (node, HMAC)  body {reason}
+func (h *SnapshotJobHandler) Fail(c *gin.Context) {
+	id, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		c.JSON(http.StatusBadRequest, models.APIError{Code: "bad_request", Message: "invalid id"})
+		return
+	}
+	var req struct {
+		Reason string `json:"reason"`
+	}
+	_ = c.ShouldBindJSON(&req)
+	if req.Reason == "" {
+		req.Reason = "snapshot failed"
+	}
+	if err := h.store.SetSnapshotError(c.Request.Context(), id, req.Reason); err != nil {
+		c.JSON(http.StatusInternalServerError, models.APIError{Code: "internal_error", Message: err.Error()})
+		return
+	}
+	c.Status(http.StatusNoContent)
+}