fix: 恢复被误回退的后端文件（#1519 #1520）

apps/worker/video_processing/thumbnail_generator.py

@@ -278,6 +278,7 @@ def extract_and_upload_cover_frames(
     video_path: str,
     plan_id: str,
     *,
+    task_id: str = "",
     num_frames: int = 3,
     title_text: str = "",
     title_color: str = "#ffffff",
@@ -291,6 +292,7 @@ def extract_and_upload_cover_frames(
     Args:
         video_path: 视频文件路径
         plan_id: 编辑计划 ID（用于生成 storage key）
+        task_id: 任务 ID（用于生成独立的 storage key，避免标题变更时封面冲突）
         num_frames: 抽取帧数（默认 3）
         title_text: 标题文字；非空时用 Pillow 叠加到每帧。
             从已渲染视频抽帧时通常传空（标题已烧录）；从源素材抽帧时传标题。
@@ -338,7 +340,7 @@ def extract_and_upload_cover_frames(
                         font_size=title_font_size,
                     )
 
-                storage_key = f"covers/{plan_id}/mediakit_frame_{i}.jpg"
+                storage_key = f"covers/{plan_id}/{task_id}/mediakit_frame_{i}.jpg"
                 url = upload_to_oss(tmp.name, storage_key)
                 if url:
                     seek_time = frame.get("timestamp", 0.0)
@@ -377,7 +379,7 @@ def extract_and_upload_cover_frames(
                     position=title_position,
                     font_size=title_font_size,
                 )
-            storage_key = f"covers/{plan_id}/frame_{i}.jpg"
+            storage_key = f"covers/{plan_id}/{task_id}/frame_{i}.jpg"
             url = upload_to_oss(frame_path, storage_key)
             if url:
                 seek_time = max(0.5, duration * ratio) if duration > 0 else 0.0