feat: HR Portal - Complete Multi-Tenant System with Redis Session Storage

Major Features:
- ✅ Multi-tenant architecture (tenant isolation)
- ✅ Employee CRUD with lifecycle management (onboarding/offboarding)
- ✅ Department tree structure with email domain management
- ✅ Company info management (single-record editing)
- ✅ System functions CRUD (permission management)
- ✅ Email account management (multi-account per employee)
- ✅ Keycloak SSO integration (auth.lab.taipei)
- ✅ Redis session storage (10.1.0.254:6379)
  - Solves Cookie 4KB limitation
  - Cross-system session sharing
  - Sliding expiration (8 hours)
  - Automatic token refresh

Technical Stack:
Backend:
- FastAPI + SQLAlchemy
- PostgreSQL 16 (10.1.0.20:5433)
- Keycloak Admin API integration
- Docker Mailserver integration (SSH)
- Alembic migrations

Frontend:
- Next.js 14 (App Router)
- NextAuth 4 with Keycloak Provider
- Redis session storage (ioredis)
- Tailwind CSS

Infrastructure:
- Redis 7 (10.1.0.254:6379) - Session + Cache
- Keycloak 26.1.0 (auth.lab.taipei)
- Docker Mailserver (10.1.0.254)

Architecture Highlights:
- Session管理由 Keycloak + Redis 統一控制
- 支援多系統 (HR/WebMail/Calendar/Drive/Office) 共享 session
- Token 自動刷新,異質服務整合
- 未來可無縫遷移到雲端

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

docker-compose.dev.yml

@@ -0,0 +1,41 @@
+version: '3.8'
+
+services:
+  # 後端 API (開發模式)
+  backend:
+    build:
+      context: ./backend
+      dockerfile: Dockerfile.dev
+    container_name: hr-portal-backend-dev
+    ports:
+      - "10181:10181"
+    environment:
+      - ENVIRONMENT=development
+      - DATABASE_URL=postgresql+psycopg://hr_admin:hr_dev_password_2026@10.1.0.20:5433/hr_portal
+      - API_BASE_URL=http://localhost:10181
+      - CORS_ORIGINS=http://localhost:10180,http://10.1.0.245:10180
+    networks:
+      - hr-network
+    restart: unless-stopped
+
+  # 前端應用 (開發模式)
+  frontend:
+    build:
+      context: ./frontend
+      dockerfile: Dockerfile.dev
+    container_name: hr-portal-frontend-dev
+    ports:
+      - "10180:10180"
+    environment:
+      - NEXT_PUBLIC_API_BASE_URL=http://localhost:10181/api/v1
+      - NEXTAUTH_URL=http://localhost:10180
+      - NEXTAUTH_SECRET=development-secret-key-change-in-production
+    networks:
+      - hr-network
+    depends_on:
+      - backend
+    restart: unless-stopped
+
+networks:
+  hr-network:
+    driver: bridge