[GF-FE-19] Add Google Calendar sync and Outlook .ics download to booking pages

[yusuftomilola]

Problem

Members must manually copy booking details into their calendar apps. There is no "Add to Calendar" button after a booking is confirmed, and no way to connect a Google Calendar account to auto-sync future bookings. The calendar sync backend (GF-BE-15) handles OAuth and sync logic but has no frontend connection.

Proposed Solution

Add calendar sync UI in two places.

1. Booking confirmation and detail page (frontend/app/bookings/[id]/page.tsx)

• Add an "Add to Google Calendar" button that triggers the OAuth connect flow if not already connected, or directly creates the calendar event if connected
• Add an "Add to Outlook" button that generates and downloads an .ics file (this can be done client-side without any backend endpoint using the ics npm package)

2. Profile settings (frontend/app/profile/page.tsx or frontend/app/settings/page.tsx)

• Add a Calendar Sync section showing connection status
• Connect Google Calendar button → calls GET /calendar-sync/auth/google to get the OAuth URL, then redirects the user
• Disconnect button → calls DELETE /calendar-sync/disconnect
• Status indicator: "Connected ✓" or "Not connected"

Acceptance Criteria

• "Add to Google Calendar" button added to the booking detail page
• Clicking the button redirects to Google OAuth if not connected, or creates the event directly if already connected
• "Add to Outlook" button generates and downloads an .ics file (client-side, no backend required)
• Calendar sync status section added to profile/settings
• Connect and Disconnect buttons call the correct API endpoints
• ics npm package used for Outlook .ics generation

Depends on: [GF-BE-15] Build Google Calendar OAuth and booking sync service