feat: auto-sync file list + clear processing cache

- Auto-sync file_relations on every query (files appear immediately)
- Add POST /api/files/reset-cache endpoint to delete output/result
  files and reset status to pending for reprocessing
- Add "清除处理缓存" button to all 3 file views

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/backend/routers/files.py

@@ -15,7 +15,7 @@ from ..config import MAX_UPLOAD_SIZE, ALLOWED_EXTENSIONS
 from ..services.db_schema import (
     insert_file_metadata, query_file_history, query_file_stats,
     query_file_relations, delete_file_relations, sync_file_relations,
-    query_file_relations_stats,
+    query_file_relations_stats, reset_file_cache,
 )
 
 logger = logging.getLogger(__name__)
@@ -301,9 +301,12 @@ async def get_file_relations(
     page_size: int = Query(50, ge=1, le=200),
     sort_by: Optional[str] = None,
     sort_order: str = "desc",
+    sync: bool = Query(True, description="Auto-sync file relations before querying"),
     current_user: dict = Depends(get_current_user),
 ):
     """Query file relations with optional view filter."""
+    if sync:
+        sync_file_relations()
     items, total = query_file_relations(view=view, status=status, page=page, page_size=page_size,
                                         sort_by=sort_by, sort_order=sort_order)
     return {"items": items, "total": total}
@@ -326,6 +329,24 @@ async def sync_relations(
     return {"message": "文件关系表已重建"}
 
 
+class ResetCacheRequest(BaseModel):
+    files: list[dict]  # [{input_image, output_excel, result_purchase}, ...]
+
+
+@router.post("/reset-cache")
+async def reset_cache(
+    req: ResetCacheRequest,
+    current_user: dict = Depends(get_current_user),
+):
+    """Delete output/result files and reset status to pending for reprocessing.
+
+    Each item in files should have: {input_image?, output_excel?, result_purchase?}
+    The corresponding files on disk are deleted, and the relation status is reset.
+    """
+    result = reset_file_cache(req.files)
+    return result
+
+
 @router.delete("/relations")
 async def delete_relations(
     body: RelationDeleteRequest,