[FE-45] Notification preferences settings page (/settings/notifications)

[yusuftomilola]

Overview

Members currently receive all notification types on all channels with no way to opt out. A notification preferences page lets members control exactly which alerts they receive and via which channels, reducing unsubscribe rates and notification fatigue.

Context

• frontend/app/settings/page.tsx — existing settings page (add a "Notifications" tab or section here)
• Depends on BE-58 for GET /notifications/preferences and PATCH /notifications/preferences
• Push notification status connects with the PWA push opt-in (FE-40)

Tasks

• Add a "Notifications" tab to the /settings page (or a sub-route /settings/notifications)
• Notification preferences UI — grouped toggle rows:
  • Booking Updates: Booking confirmed, Booking cancelled, Booking reminder
  • Payments: Payment received, Payment failed, Invoice generated
  • Community: New messages, Announcements
  • Events: Event reminders, RSVP confirmations
  • Waitlist: Spot available alerts
• Per-group: three channel toggle columns — In-App | Email | SMS
  • SMS column: show "Add phone number to enable" link if no phone on file; otherwise show toggle
  • Push column: show current push permission status; "Enable Push" button if not granted (triggers FE-40 flow)
• "Save Preferences" button at bottom calls PATCH /notifications/preferences with changed values; show success toast
• On page load, fetch current preferences and pre-fill all toggles
• Create useNotificationPreferences and useUpdateNotificationPreferences React Query hooks

Files to Modify / Create

• frontend/app/settings/page.tsx
• New: frontend/lib/react-query/hooks/notifications/useNotificationPreferences.ts
• New: frontend/lib/react-query/hooks/notifications/useUpdateNotificationPreferences.ts