Gap 13: BWF/INFO metadata cho WAV export — wav_bwf.patch_bwf_metadata chen bext + LIST/INFO (INAM/IART/ISRC/ICMT) truoc data chunk, giu nguyen PCM bits; render_project(metadata=) + RenderRequest.metadata + cloud render task; ExportModal Title/Artist/ISRC; test_66 (178 passed)

app/api/v1/projects.py

@@ -546,6 +546,7 @@ async def cleanup_all_backups(req: CleanupBackupsRequest, current_user: dict = D
 
 class RenderProjectRequest(BaseModel):
     sample_rate: Optional[int] = 44100
+    metadata: Optional[dict] = None  # Gap 13: BWF/INFO metadata (title/artist/isrc/...)
 
 @router.post("/cloud/{project_id}/render")
 async def render_project_endpoint(project_id: str, req: RenderProjectRequest, current_user: dict = Depends(get_current_user)):
@@ -568,7 +569,8 @@ async def render_project_endpoint(project_id: str, req: RenderProjectRequest, cu
         project_id=project_id,
         project_name=row["name"],
         project_json_str=row["data_json"],
-        sample_rate=req.sample_rate or 44100
+        sample_rate=req.sample_rate or 44100,
+        metadata=req.metadata or None
     )
     
     return {