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>

test_db_connection.py

@@ -0,0 +1,72 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""測試 HR Portal 資料庫連接"""
+
+import sys
+import os
+
+# 添加 backend 路徑
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'backend'))
+
+print("=" * 60)
+print("HR Portal 資料庫連接測試")
+print("=" * 60)
+
+try:
+    # 測試環境變數載入
+    print("\n[1] 載入環境變數...")
+    from dotenv import load_dotenv
+    env_path = os.path.join(os.path.dirname(__file__), 'backend', '.env')
+    load_dotenv(env_path)
+
+    db_url = os.getenv('DATABASE_URL')
+    print(f"  DATABASE_URL: {db_url[:50]}...")
+
+    # 測試資料庫連接
+    print("\n[2] 測試資料庫連接...")
+    from sqlalchemy import create_engine, text
+
+    engine = create_engine(db_url, echo=False)
+
+    with engine.connect() as conn:
+        # 測試基本查詢
+        result = conn.execute(text("SELECT version();"))
+        version = result.fetchone()[0]
+        print(f"  [OK] PostgreSQL 版本: {version[:50]}...")
+
+        # 檢查資料表
+        result = conn.execute(text("""
+            SELECT tablename
+            FROM pg_tables
+            WHERE schemaname = 'public'
+            ORDER BY tablename
+        """))
+        tables = [row[0] for row in result.fetchall()]
+        print(f"\n[3] 資料表列表 ({len(tables)} 個):")
+        for table in tables:
+            result = conn.execute(text(f'SELECT COUNT(*) FROM "{table}"'))
+            count = result.fetchone()[0]
+            print(f"  - {table:30} {count:>6} 筆")
+
+    print("\n[4] 測試 Alembic 連接...")
+    from alembic.config import Config
+    from alembic import command
+
+    alembic_cfg = Config(os.path.join(os.path.dirname(__file__), 'backend', 'alembic.ini'))
+    alembic_cfg.set_main_option('script_location', os.path.join(os.path.dirname(__file__), 'backend', 'alembic'))
+
+    # 檢查當前版本
+    with engine.connect() as conn:
+        result = conn.execute(text("SELECT version_num FROM alembic_version"))
+        current_version = result.fetchone()[0]
+        print(f"  當前 Alembic 版本: {current_version}")
+
+    print("\n" + "=" * 60)
+    print("資料庫連接測試成功!")
+    print("=" * 60)
+
+except Exception as e:
+    print(f"\n[FAIL] 測試失敗: {e}")
+    import traceback
+    traceback.print_exc()
+    sys.exit(1)