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/api/v1/schedules.py

@@ -0,0 +1,69 @@
+from typing import List
+from datetime import datetime
+from fastapi import APIRouter, Depends, HTTPException, BackgroundTasks
+from sqlalchemy.orm import Session
+from croniter import croniter
+
+from app.core.database import get_db
+from app.models.schedule import Schedule
+from app.schemas.schedule import ScheduleResponse, ScheduleUpdate, ScheduleLogResponse
+
+router = APIRouter(prefix="/schedules", tags=["schedules"])
+
+
+@router.get("", response_model=List[ScheduleResponse])
+def list_schedules(db: Session = Depends(get_db)):
+    return db.query(Schedule).order_by(Schedule.id).all()
+
+
+@router.get("/{schedule_id}", response_model=ScheduleResponse)
+def get_schedule(schedule_id: int, db: Session = Depends(get_db)):
+    s = db.get(Schedule, schedule_id)
+    if not s:
+        raise HTTPException(status_code=404, detail="Schedule not found")
+    return s
+
+
+@router.put("/{schedule_id}", response_model=ScheduleResponse)
+def update_schedule_cron(schedule_id: int, payload: ScheduleUpdate, db: Session = Depends(get_db)):
+    s = db.get(Schedule, schedule_id)
+    if not s:
+        raise HTTPException(status_code=404, detail="Schedule not found")
+    # Validate cron expression
+    try:
+        cron = croniter(payload.cron_timer, datetime.utcnow())
+        next_run = cron.get_next(datetime)
+    except Exception:
+        raise HTTPException(status_code=422, detail="Invalid cron expression")
+    s.cron_timer = payload.cron_timer
+    s.next_run_at = next_run
+    db.commit()
+    db.refresh(s)
+    return s
+
+
+@router.post("/{schedule_id}/run", status_code=202)
+def manual_run(schedule_id: int, background_tasks: BackgroundTasks, db: Session = Depends(get_db)):
+    """手動觸發排程（非同步執行）"""
+    s = db.get(Schedule, schedule_id)
+    if not s:
+        raise HTTPException(status_code=404, detail="Schedule not found")
+    if s.status == "Going":
+        raise HTTPException(status_code=409, detail="Schedule is already running")
+
+    from app.services.scheduler.runner import dispatch_schedule
+    background_tasks.add_task(dispatch_schedule, schedule_id)
+    return {"message": f"Schedule '{s.name}' triggered", "schedule_id": schedule_id}
+
+
+@router.get("/{schedule_id}/logs", response_model=List[ScheduleLogResponse])
+def get_schedule_logs(schedule_id: int, limit: int = 20, db: Session = Depends(get_db)):
+    from app.models.schedule import ScheduleLog
+    logs = (
+        db.query(ScheduleLog)
+        .filter(ScheduleLog.schedule_id == schedule_id)
+        .order_by(ScheduleLog.started_at.desc())
+        .limit(limit)
+        .all()
+    )
+    return logs