feat: add StationTaggingService with supermarket detection

tests/Unit/Services/StationTaggingServiceTest.php

@@ -0,0 +1,68 @@
+<?php
+
+use App\Models\Station;
+use App\Services\StationTaggingService;
+
+beforeEach(function (): void {
+    $this->service = new StationTaggingService();
+});
+
+it('marks tesco station as supermarket and normalises brand', function (): void {
+    $station = new Station([
+        'trading_name' => 'TESCO EXTRA',
+        'is_supermarket' => false,
+    ]);
+
+    $this->service->tag($station);
+
+    expect($station->is_supermarket)->toBeTrue()
+        ->and($station->brand_name)->toBe('Tesco');
+});
+
+it('marks asda station as supermarket', function (): void {
+    $station = new Station([
+        'trading_name' => 'Asda Petrol Station',
+        'is_supermarket' => false,
+    ]);
+
+    $this->service->tag($station);
+
+    expect($station->is_supermarket)->toBeTrue()
+        ->and($station->brand_name)->toBe('Asda');
+});
+
+it('does not mark independent station as supermarket', function (): void {
+    $station = new Station([
+        'trading_name' => 'Village Garage',
+        'is_supermarket' => false,
+    ]);
+
+    $this->service->tag($station);
+
+    expect($station->is_supermarket)->toBeFalse();
+});
+
+it('handles case insensitive matching', function (): void {
+    $station = new Station([
+        'trading_name' => 'morrisons petrol',
+        'is_supermarket' => false,
+    ]);
+
+    $this->service->tag($station);
+
+    expect($station->is_supermarket)->toBeTrue()
+        ->and($station->brand_name)->toBe('Morrisons');
+});
+
+it('does not overwrite brand_name for non-supermarket stations', function (): void {
+    $station = new Station([
+        'trading_name'   => 'Shell Garage',
+        'brand_name'     => 'Shell',
+        'is_supermarket' => false,
+    ]);
+
+    $this->service->tag($station);
+
+    expect($station->is_supermarket)->toBeFalse()
+        ->and($station->brand_name)->toBe('Shell');
+});