fix: stream Blender frame output to frontend for cinematic renders

The filter only matched [cinematic_render] tag but Blender outputs its
own "Saved: frame_NNNN.png" lines per frame. Now also matches "Saved:"
lines, extracts the frame number, and formats as:
  [cinematic_render] Frame 84/480 rendered

This shows live frame progress in the LiveRenderLog on the frontend.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/render_blender.py

@@ -674,10 +674,18 @@ def render_cinematic_to_file(
                 line = line.rstrip("\n")
                 if key.data == "stdout":
                     logger.info("[cinematic] %s", line)
-                    if "[cinematic_render]" in line:
+                    if "[cinematic_render]" in line or "Saved:" in line:
                         log_lines.append(line)
                         if log_callback:
-                            log_callback(line)
+                            # For Blender "Saved:" lines, format as frame progress
+                            if "Saved:" in line and "frame_" in line:
+                                import re as _re
+                                m = _re.search(r'frame_(\d+)', line)
+                                if m:
+                                    fnum = int(m.group(1))
+                                    log_callback(f"[cinematic_render] Frame {fnum}/480 rendered")
+                            else:
+                                log_callback(line)
                 else:
                     stderr_lines.append(line)
                     logger.warning("[cinematic stderr] %s", line)