feat(backend): Phase 1-4 全新開發完成，37/37 TDD 通過

[Phase 0 Reset]
- 清除舊版 app/、alembic/versions/、雜亂測試腳本
- 新 requirements.txt (移除 caldav/redis/keycloak-lib，加入 apscheduler/croniter/docker/paramiko/ping3/dnspython)

[Phase 1 資料庫]
- 9 張資料表 SQLAlchemy Models：tenants / accounts / schedules / schedule_logs /
  tenant_schedule_results / account_schedule_results / servers / server_status_logs / system_status_logs
- Alembic migration 001_create_all_tables (已套用到 10.1.0.20:5433/virtual_mis)
- seed.py：schedules 初始 3 筆 / servers 初始 4 筆

[Phase 2 CRUD API]
- GET/POST/PUT/DELETE: /api/v1/tenants / accounts / servers / schedules
- /api/v1/system-status
- 帳號編碼自動產生 (prefix + seq_no 4碼左補0)
- 燈號 (lights) 從最新排程結果取得

[Phase 3 Watchdog]
- APScheduler interval 3分鐘，原子 UPDATE status=Going 防重複執行
- 手動觸發 API: POST /api/v1/schedules/{id}/run

[Phase 4 Service Clients]
- KeycloakClient：vmis-admin realm，REST API (不用 python-keycloak)
- MailClient：Docker Mailserver @ 10.1.0.254:8080，含 MX DNS 驗證
- DockerClient：docker-py 本機 + paramiko SSH 遠端 compose
- NextcloudClient：OCS API user/quota
- SystemChecker：功能驗證 (traefik routers>0 / keycloak token / SMTP EHLO / DB SELECT 1 / ping)

[TDD]
- 37 tests / 37 passed (2.11s)
- SQLite in-memory + StaticPool，無需外部 DB

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/tenant.py

@@ -0,0 +1,71 @@
+from datetime import date, datetime
+from typing import Optional
+from pydantic import BaseModel, EmailStr
+
+
+class TenantBase(BaseModel):
+    code: str
+    prefix: str = ""
+    name: str
+    name_eng: Optional[str] = None
+    tax_id: Optional[str] = None
+    domain: str
+    address: Optional[str] = None
+    tel: Optional[str] = None
+    contact: Optional[str] = None
+    contact_mobile: Optional[str] = None
+    contact_email: Optional[str] = None
+    keycloak_realm: Optional[str] = None
+    plan_code: Optional[str] = None
+    employee_limit: Optional[int] = None
+    trial_start_date: Optional[date] = None
+    trial_end_date: Optional[date] = None
+    quota_per_user: int = 20
+    total_quota: int = 200
+    is_manager: bool = False
+    is_active: bool = True
+    status: str = "trial"
+    note: Optional[str] = None
+
+
+class TenantCreate(TenantBase):
+    pass
+
+
+class TenantUpdate(BaseModel):
+    name: Optional[str] = None
+    name_eng: Optional[str] = None
+    tax_id: Optional[str] = None
+    domain: Optional[str] = None
+    address: Optional[str] = None
+    tel: Optional[str] = None
+    contact: Optional[str] = None
+    contact_mobile: Optional[str] = None
+    contact_email: Optional[str] = None
+    plan_code: Optional[str] = None
+    employee_limit: Optional[int] = None
+    trial_start_date: Optional[date] = None
+    trial_end_date: Optional[date] = None
+    quota_per_user: Optional[int] = None
+    total_quota: Optional[int] = None
+    is_active: Optional[bool] = None
+    status: Optional[str] = None
+    note: Optional[str] = None
+
+
+class TenantStatusLight(BaseModel):
+    sso_result: Optional[bool] = None
+    mailbox_result: Optional[bool] = None
+    nc_result: Optional[bool] = None
+    office_result: Optional[bool] = None
+    quota_usage: Optional[float] = None
+
+
+class TenantResponse(TenantBase):
+    id: int
+    created_at: datetime
+    updated_at: datetime
+    lights: Optional[TenantStatusLight] = None
+
+    class Config:
+        from_attributes = True