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>

database/migrations/2026_04_10_170504_add_preferred_fuel_type_to_users_table.php

@@ -0,0 +1,29 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('users', function (Blueprint $table): void {
+            $table->string('preferred_fuel_type', 20)->default('petrol')->after('postcode')
+                ->comment('User\'s default fuel type for homepage search');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('users', function (Blueprint $table): void {
+            $table->dropColumn('preferred_fuel_type');
+        });
+    }
+};

database/migrations/2026_04_10_170504_create_saved_stations_table.php

@@ -0,0 +1,32 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('saved_stations', function (Blueprint $table): void {
+            $table->id();
+            $table->foreignId('user_id')->constrained()->cascadeOnDelete();
+            $table->string('station_id', 64);
+            $table->timestamps();
+
+            $table->unique(['user_id', 'station_id']);
+            $table->index(['user_id']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('saved_stations');
+    }
+};