Wire dialog to consent service and handle decision

Create a ConsentStatusNotifier extending AsyncNotifier that fetches initial status from the consent service on build() and exposes grant() and deny() methods. The parent widget (map feature guard) watches this provider and shows the dialog using showDialog only when status is ConsentStatus.pending. Pass onOptIn and onOptOut callbacks from the parent to the dialog widget — in onOptIn, call notifier.grant(), await it, then navigate. Use GoRouter's redirect or a guard widget rather than imperative navigation to ensure map routes are unreachable when status is not granted.

Avoid storing consent status in flutter_secure_storage — the Supabase database is the authoritative store; the Riverpod provider is just a runtime cache. For the loading state inside buttons, use a local ValueNotifier isLoading rather than lifting loading state to the Riverpod provider to keep the provider's state semantically clean.

Unit tests using ProviderContainer: mock location-consent-service, simulate Opt In tap → assert grantConsent called with correct args, assert provider transitions to granted. Simulate Opt Out → assert recordDenial called, provider transitions to denied. Simulate service failure → assert provider stays in previous state, error is surfaced. Widget integration test: render the parent screen with a mock provider, assert dialog is shown when status is pending, assert dialog is NOT shown when status is granted.

Test navigation: use a NavigatorObserver mock to assert correct route pushed after each decision. Test double-tap prevention: simulate rapid double-tap on Opt In and assert grantConsent called exactly once.