feat: add data backup/import, goal step ordering, and PostgreSQL migration

- Add GET /api/backup/export and POST /api/backup/import endpoints for full data backup
- Add drag-and-drop reorder for goal steps with PUT /api/goals/{id}/steps/reorder
- Auto-assign sort_order on step creation (preserves creation order)
- Fix duplicate milestone rendering in goal detail page
- Add category management button in goal dialog
- Migrate database default from SQLite to PostgreSQL
- Fix router guard redirect loop for logged-in users on setup/login pages
- Fix ALTER TABLE ADD COLUMN crash on callable defaults (uuid.uuid4)
- Add auth status rate limiter and token version caching
- Update CLAUDE.md to reflect current architecture

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/app/config.py

@@ -9,8 +9,10 @@ _logger = logging.getLogger("app.config")
 _BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
 # 数据库配置
-DATABASE_PATH = os.path.join(_BASE_DIR, "data", "todo.db")
-DATABASE_URL = f"sqlite:///{DATABASE_PATH}"
+DATABASE_URL = os.getenv(
+    "DATABASE_URL",
+    "postgresql://ToDoList:53N2PTSjMBPDy6zY@192.168.1.86:5432/ToDoList",
+)
 
 # WebUI 配置
 WEBUI_PATH = os.path.join(_BASE_DIR, "webui")
@@ -49,3 +51,4 @@ def _load_jwt_secret() -> str:
 
 JWT_SECRET = _load_jwt_secret()
 ACCESS_TOKEN_EXPIRE_MINUTES = 1440  # 24小时
+ACCESS_TOKEN_EXPIRE_SECONDS = ACCESS_TOKEN_EXPIRE_MINUTES * 60