feat: implement user authentication module

- Backend (FastAPI):
  - External API authentication (pj-auth-api.vercel.app)
  - JWT token validation with Redis session storage
  - RBAC with department isolation
  - User, Role, Department models with pjctrl_ prefix
  - Alembic migrations with project-specific version table
  - Complete test coverage (13 tests)

- Frontend (React + Vite):
  - AuthContext for state management
  - Login page with error handling
  - Protected route component
  - Dashboard with user info display

- OpenSpec:
  - 7 capability specs defined
  - add-user-auth change archived

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/schemas/__init__.py

@@ -0,0 +1,18 @@
+from app.schemas.auth import LoginRequest, LoginResponse, TokenPayload
+from app.schemas.user import UserCreate, UserUpdate, UserResponse, UserInDB
+from app.schemas.department import DepartmentCreate, DepartmentUpdate, DepartmentResponse
+from app.schemas.role import RoleResponse
+
+__all__ = [
+    "LoginRequest",
+    "LoginResponse",
+    "TokenPayload",
+    "UserCreate",
+    "UserUpdate",
+    "UserResponse",
+    "UserInDB",
+    "DepartmentCreate",
+    "DepartmentUpdate",
+    "DepartmentResponse",
+    "RoleResponse",
+]