fix(lint): 修复 PR #14 引入的 lint 回退 (119→0)

PR #14 从旧分支复制文件导致回退了 PR #10 的 lint 修复。
修复内容:
- autoflake 移除未使用导入/变量
- autopep8 修复缩进/空格
- 手动修复 F821(pathlib→Path), F541(f-string), F841(未使用变量)
- 所有修复均通过 flake8 --max-line-length=120 --extend-ignore=E501 检查 (0 errors)

src/blackboard/registry.py

@@ -119,7 +119,8 @@ class ProjectRegistry:
         finally:
             conn.close()
 
-    def list_projects(self, status: Optional[str] = None) -> Dict[str, Dict[str, Any]]:
+    def list_projects(
+            self, status: Optional[str] = None) -> Dict[str, Dict[str, Any]]:
         """列出项目"""
         conn = self._connect()
         try:
@@ -178,7 +179,8 @@ class ProjectRegistry:
             status="deleted",
         )
 
-    def physical_delete_project(self, project_id: str) -> Optional[Dict[str, Any]]:
+    def physical_delete_project(
+            self, project_id: str) -> Optional[Dict[str, Any]]:
         """物理删除项目（删目录 + 删 registry 条目）"""
         import shutil
 
@@ -260,7 +262,8 @@ class ProjectRegistry:
     # 迁移（从 _registry.yaml）
     # ===================================================================
 
-    def discover_sanguo_projects(self, scan_dir: Optional[Path] = None) -> List[str]:
+    def discover_sanguo_projects(
+            self, scan_dir: Optional[Path] = None) -> List[str]:
         """扫描 sanguo_projects 开发目录，自动注册正式项目"""
         scan_dir = scan_dir or Path(os.environ.get(
             "SANGUO_PROJECTS_DIR",
@@ -355,4 +358,3 @@ class ProjectRegistry:
 
     def reload(self) -> None:
         """兼容旧接口（SQLite 不需要 reload cache）"""
-        pass