feat: add user preferences and saved stations API endpoints

Adds authenticated endpoints for reading/updating fuel type preferences and managing saved stations, backed by new migrations and a SavedStation model.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Models/SavedStation.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+
+final class SavedStation extends Model
+{
+    protected $fillable = ['user_id', 'station_id'];
+}

app/Models/User.php

@@ -9,13 +9,14 @@ use Filament\Panel;
 use Illuminate\Database\Eloquent\Attributes\Fillable;
 use Illuminate\Database\Eloquent\Attributes\Hidden;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Foundation\Auth\User as Authenticatable;
 use Illuminate\Notifications\Notifiable;
 use Illuminate\Support\Str;
 use Laravel\Fortify\TwoFactorAuthenticatable;
 use Laravel\Sanctum\HasApiTokens;
 
-#[Fillable(['name', 'email', 'password', 'is_admin', 'postcode'])]
+#[Fillable(['name', 'email', 'password', 'is_admin', 'postcode', 'preferred_fuel_type'])]
 #[Hidden(['password', 'two_factor_secret', 'two_factor_recovery_codes', 'remember_token'])]
 class User extends Authenticatable implements FilamentUser
 {
@@ -52,4 +53,9 @@ class User extends Authenticatable implements FilamentUser
             ->map(fn ($word) => Str::substr($word, 0, 1))
             ->implode('');
     }
+
+    public function savedStations(): HasMany
+    {
+        return $this->hasMany(SavedStation::class);
+    }
 }