fix: auto-fix code issues (cron)

- 修复重复导入/字段
- 修复异常处理（将裸 except: 改为具体异常类型）
- 修复PEP8格式问题
- 添加类型注解

backend/search_manager.py

@@ -374,7 +374,7 @@ class FullTextSearch:
         # 排序和分页
         scored_results.sort(key=lambda x: x.score, reverse=True)
 
-        return scored_results[offset : offset + limit]
+        return scored_results[offset: offset + limit]
 
     def _parse_boolean_query(self, query: str) -> dict:
         """
@@ -574,7 +574,7 @@ class FullTextSearch:
                 return None
 
             return row["project_id"] if row else None
-        except Exception:
+        except (sqlite3.Error, KeyError):
             return None
 
     def _score_results(self, results: list[dict], parsed_query: dict) -> list[SearchResult]:
@@ -1078,7 +1078,7 @@ class SemanticSearch:
                         metadata={},
                     )
                 )
-            except Exception:
+            except (KeyError, ValueError):
                 continue
 
         results.sort(key=lambda x: x.similarity, reverse=True)