Add tier feature design spec, annual billing, fuel type normalization, and admin subscription management

- Add comprehensive tier feature matrix spec defining Free/Basic/Plus/Pro capabilities across recommendations, predictions, history, logs, tools, and family sharing
- Add `stripe_price_id_annual` column to plans table and rename existing column to `stripe_price_id_monthly`
- Normalize legacy fuel type aliases (petrol→e10, diesel→b7_standard) in users table
- Implement BillingController with checkout, portal, success/cancel routes supporting monthly/annual cadence
- Add admin subscription assignment in Filament user edit page with admin-granted subscription support
- Add DowngradeUserOnSubscriptionDeleted listener to disable WhatsApp/SMS preferences on subscription cancellation
- Add MissedNotificationsOverview widget to Filament user detail page
- Add PollFuelPricesTest covering auto-refresh scenarios
- Add PriceReliability enum with reliability classification based on price age
- Add fuelTypes.js constants file exporting FUEL_TYPES from window global

resources/js/constants/fuelTypes.js

@@ -0,0 +1,9 @@
+// Canonical fuel type labels come from PHP enum App\Enums\FuelType.
+// They are injected into window.FUEL_TYPES by resources/views/app.blade.php
+// so both backend (Filament forms, notifications) and frontend share one source.
+
+export const FUEL_TYPES = window.FUEL_TYPES ?? []
+
+export const FUEL_TYPE_LABELS = Object.fromEntries(
+    FUEL_TYPES.map((t) => [t.value, t.label]),
+)