feat(render #36): real per-tier output height (360/540/720/1080/4K)

r_height was hardcoded 1080. render-svc now derives r_height from the resolution
(ResolutionHeight) on job create; node-agent ffmpeg downscales to the tier height
(scale=-2:H). Quality picker now actually changes output size.

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

services/render/internal/db/db.go

@@ -3,6 +3,7 @@ package db
 import (
 	"context"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/flatrender/render-svc/internal/models"
@@ -410,6 +411,25 @@ func (s *Store) ListActiveJobs(ctx context.Context, userID uuid.UUID) ([]*models
 	return out, rows.Err()
 }
 
+// ResolutionHeight maps a quality-tier label to its output height in pixels.
+// Used for r_height (stored) and the node's ffmpeg downscale.
+func ResolutionHeight(resolution string) int {
+	switch strings.ToLower(strings.TrimSpace(resolution)) {
+	case "360p":
+		return 360
+	case "540p":
+		return 540
+	case "720p":
+		return 720
+	case "1080p", "fullhd":
+		return 1080
+	case "4k", "2160p":
+		return 2160
+	default:
+		return 1080
+	}
+}
+
 func (s *Store) CreateJob(ctx context.Context, userID, tenantID uuid.UUID, req *models.RenderJobCreateRequest) (*models.RenderJob, error) {
 	priceType := "Free"
 	if req.PriceType != nil {
@@ -436,12 +456,12 @@ func (s *Store) CreateJob(ctx context.Context, userID, tenantID uuid.UUID, req *
 		        -- to the saved-project id only if the lookup is somehow null.
 		        COALESCE((SELECT original_project_id FROM studio.saved_projects WHERE id = $3), $3),
 		        'paid'::render_priority_queue, 'Queued'::render_step, $4::price_kind,
-		        $5::render_quality, $6, 1080, $7, COALESCE($8, FALSE),
+		        $5::render_quality, $6, $11, $7, COALESCE($8, FALSE),
 		        0, 'FIX', $9, $10)
 		RETURNING id`,
 		tenantID, userID, req.SavedProjectID, priceType,
 		req.Quality, req.Resolution, frameRate, req.Is60FPS,
-		tellMe, req.PreferredRegion,
+		tellMe, req.PreferredRegion, ResolutionHeight(req.Resolution),
 	).Scan(&id)
 	if err != nil {
 		return nil, err