多文件上传累积模式，前端文件列表支持删除，后端接收前端指定的文件列表

web/main.py

@@ -356,6 +356,7 @@ def run_analysis_task(session_id: str, files: list, user_requirement: str, is_fo
 class StartRequest(BaseModel):
     requirement: str
     template: Optional[str] = None
+    files: Optional[List[str]] = None
 
 class ChatRequest(BaseModel):
     session_id: str
@@ -383,10 +384,15 @@ async def upload_files(files: list[UploadFile] = File(...)):
 async def start_analysis(request: StartRequest, background_tasks: BackgroundTasks):
     session_id = session_manager.create_session()
     
-    # Use only the most recently uploaded files, not everything in uploads/
-    files = getattr(app.state, 'last_uploaded_files', None)
+    # Priority: request.files (from frontend) > last_uploaded > scan uploads/
+    files = None
+    if request.files:
+        files = [f for f in request.files if os.path.exists(f)]
+    if not files:
+        files = getattr(app.state, 'last_uploaded_files', None)
+        if files:
+            files = [f for f in files if os.path.exists(f)]
     if not files:
-        # Fallback: scan uploads directory
         files = glob.glob("uploads/*.csv") + glob.glob("uploads/*.xlsx")
     if not files:
         raise HTTPException(status_code=400, detail="No data files found. Please upload files first.")