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/environment.yml

@@ -0,0 +1,24 @@
+name: pjctrl
+channels:
+  - defaults
+  - conda-forge
+dependencies:
+  - python=3.11
+  - pip
+  - pip:
+    - fastapi==0.109.0
+    - uvicorn[standard]==0.27.0
+    - sqlalchemy==2.0.25
+    - pymysql==1.1.0
+    - cryptography==42.0.0
+    - alembic==1.13.1
+    - redis==5.0.1
+    - python-jose[cryptography]==3.3.0
+    - passlib[bcrypt]==1.7.4
+    - python-dotenv==1.0.0
+    - httpx==0.26.0
+    - pydantic==2.5.3
+    - pydantic-settings==2.1.0
+    - pytest==7.4.4
+    - pytest-asyncio==0.23.3
+    - pytest-cov==4.1.0