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

app/Filament/Resources/UserResource/Widgets/MissedNotificationsOverview.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace App\Filament\Resources\UserResource\Widgets;
+
+use App\Models\NotificationLog;
+use App\Models\User;
+use Filament\Widgets\StatsOverviewWidget;
+use Filament\Widgets\StatsOverviewWidget\Stat;
+
+class MissedNotificationsOverview extends StatsOverviewWidget
+{
+    public ?User $record = null;
+
+    protected function getStats(): array
+    {
+        if ($this->record === null) {
+            return [];
+        }
+
+        $userId = $this->record->id;
+
+        $missedTodayByChannel = fn (string $channel): int => NotificationLog::where('user_id', $userId)
+            ->where('channel', $channel)
+            ->where('sent', false)
+            ->whereDate('created_at', today())
+            ->count();
+
+        $missedThisMonth = NotificationLog::where('user_id', $userId)
+            ->where('sent', false)
+            ->whereMonth('created_at', now()->month)
+            ->whereYear('created_at', now()->year)
+            ->count();
+
+        return [
+            Stat::make('SMS missed today', $missedTodayByChannel('sms'))
+                ->color($missedTodayByChannel('sms') > 0 ? 'warning' : 'gray'),
+            Stat::make('WhatsApp missed today', $missedTodayByChannel('whatsapp'))
+                ->color($missedTodayByChannel('whatsapp') > 0 ? 'warning' : 'gray'),
+            Stat::make('Total missed this month', $missedThisMonth)
+                ->color($missedThisMonth > 0 ? 'warning' : 'gray'),
+        ];
+    }
+}