fix(render): node reports progress → moving bar + ETA (was stuck 0%/Preparing)

The node's onProgress callback only LOGGED — it never POSTed, so render_progress stayed
0 and step stayed Preparing (no bar, no ETA). Add render-svc POST
/v1/internal/render/jobs/{id}/progress (UpdateJobProgress: set render_progress + bump
step Queued/Preparing→Rendering once >0) + client UpdateProgress + wire onProgress to
post it (8s best-effort timeout, AE-CPU/DB-starvation tolerant). Preview already posts;
real-frame preview is epic C.

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

services/node-agent/internal/client/client.go

@@ -357,6 +357,22 @@ func (c *Client) UpdatePreview(ctx context.Context, jobID, imageB64 string) erro
 	return nil
 }
 
+// UpdateProgress reports the render percentage so the UI shows a moving bar + ETA.
+// Errors are non-fatal — the UI just won't advance.
+func (c *Client) UpdateProgress(ctx context.Context, jobID string, percent int) error {
+	resp, err := c.do(ctx, http.MethodPost,
+		fmt.Sprintf("/v1/internal/render/jobs/%s/progress", jobID),
+		map[string]int{"progress": percent})
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode >= 300 {
+		return fmt.Errorf("progress: HTTP %d", resp.StatusCode)
+	}
+	return nil
+}
+
 // GetOutputUploadURL asks the orchestrator to allocate an Export row and
 // return a presigned MinIO PUT URL for the rendered output file.
 func (c *Client) GetOutputUploadURL(ctx context.Context, jobID string) (*OutputUploadURLResponse, error) {