feat: notifications API, auto-jobs, calendar housekeeping fixes

Backend:
- notifications table (024 migration) — stores per-hotel notifications
- GET/PATCH/POST/DELETE /api/hotels/:slug/notifications endpoints
- createNotification() helper used by jobs + future hooks
- jobs.ts — background tasks every 10min: auto-cancel no-shows and
  auto-checkout overdue stays based on hotel_settings, broadcasts WS
  events and creates notifications for each automated action

Frontend:
- CalendarPage: handle housekeeping_done WS → update room status in
  calendar in real-time (bug fix)
- CalendarPage: when manually setting room to dirty via context menu,
  auto-create housekeeping task and broadcast via WS (bug fix)
- NotificationsContext: replaced mock data with real API integration,
  polls every 60s, syncs markRead/delete to backend
- SettingsPage booking section: auto-cancel no-show toggle + hours
  selector; auto-checkout toggle + hours selector
- api.ts: notifications API methods
- useHotelSocket: notification:new WS message type

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

backend/migrations/024_notifications.sql

@@ -0,0 +1,13 @@
+CREATE TABLE IF NOT EXISTS notifications (
+  id          UUID         PRIMARY KEY DEFAULT gen_random_uuid(),
+  hotel_id    UUID         NOT NULL REFERENCES hotels(id) ON DELETE CASCADE,
+  type        VARCHAR(50)  NOT NULL,
+  title       TEXT         NOT NULL,
+  body        TEXT         NOT NULL,
+  booking_id  UUID         REFERENCES bookings(id)  ON DELETE SET NULL,
+  room_id     UUID         REFERENCES rooms(id)     ON DELETE SET NULL,
+  link        TEXT,
+  is_read     BOOLEAN      NOT NULL DEFAULT false,
+  created_at  TIMESTAMPTZ  NOT NULL DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS notifications_hotel_created_idx ON notifications(hotel_id, created_at DESC);