fix: Add backend directory to Python path for proper imports

backend/main.py

@@ -6,6 +6,7 @@ ASR: 阿里云听悟 + OSS
 """
 
 import os
+import sys
 import json
 import httpx
 import uuid
@@ -17,6 +18,11 @@ from pydantic import BaseModel
 from typing import List, Optional
 from datetime import datetime
 
+# Add backend directory to path for imports
+backend_dir = os.path.dirname(os.path.abspath(__file__))
+if backend_dir not in sys.path:
+    sys.path.insert(0, backend_dir)
+
 # Import clients
 try:
     from oss_uploader import get_oss_uploader
@@ -33,7 +39,8 @@ except ImportError:
 try:
     from db_manager import get_db_manager, Project, Entity, EntityMention
     DB_AVAILABLE = True
-except ImportError:
+except ImportError as e:
+    print(f"DB import error: {e}")
     DB_AVAILABLE = False
 
 try: