Fixes red screen crash ('_dependents.isEmpty is not true') caused by
auth state change rebuilding the widget tree while the dialog was
still open and sharing the parent context across an async gap.
- Add camera, google_mlkit_text_recognition, image_picker, permission_handler deps
- Create ScannerScreen with live camera preview and OCR text recognition
- Auto-detect Hot Wheels IDs (e.g. JKF21) from captured photos using regex
- Add manual entry fallback dialog for typing HW ID by hand
- Update HomeScreen with scan FAB button and full DB query flow
- Query hotwheels table with .eq('hw_id', scannedCode).maybeSingle()
- Show 'Already in Collection' alert if car exists
- Show 'Add to Collection?' confirmation with insert if car is new
- Add supabase_flutter dependency
- Replace default counter template with auth flow (AuthGate, LoginScreen, HomeScreen)
- Implement email/password sign-in via signInWithPassword()
- Add forgot password flow with resetPasswordForEmail() and hwcollector://login deep link
- Handle PASSWORD_RECOVERY event to show set-new-password dialog
- Add deep link intent-filter to AndroidManifest for hwcollector://login scheme
- Configure Supabase URL and publishable key
- Replace outdated widget test with placeholder
