feat: localize country names in PDFs via symfony/intl (#681)

Ports #639 to 3.x — the original targets the now feature-frozen 2.x line.
Address::country_name now resolves the localized country name for the
current app locale via Symfony\Component\Intl\Countries, falling back to
the stored name on lookup failure. Adds symfony/intl + a unit test.

Co-authored-by: Lukas Selch <selchlukas@icloud.com>

tests/Unit/AddressCountryLocalizationTest.php

@@ -0,0 +1,57 @@
+<?php
+
+use App\Models\Address;
+use App\Models\Country;
+use Illuminate\Support\Facades\App;
+use Illuminate\Support\Facades\Artisan;
+
+beforeEach(function () {
+    Artisan::call('db:seed', ['--class' => 'DatabaseSeeder', '--force' => true]);
+    Artisan::call('db:seed', ['--class' => 'DemoSeeder', '--force' => true]);
+});
+
+it('returns localized country name for German locale', function () {
+    App::setLocale('de');
+
+    $address = Address::factory()->create([
+        'country_id' => Country::where('code', 'DE')->first()->id,
+    ]);
+
+    expect($address->country_name)->toBe('Deutschland');
+});
+
+it('returns localized country name for French locale', function () {
+    App::setLocale('fr');
+
+    $address = Address::factory()->create([
+        'country_id' => Country::where('code', 'DE')->first()->id,
+    ]);
+
+    expect($address->country_name)->toBe('Allemagne');
+});
+
+it('returns null when address has no country', function () {
+    $address = Address::factory()->create([
+        'country_id' => null,
+    ]);
+
+    expect($address->country_name)->toBeNull();
+});
+
+it('falls back to database name when intl lookup fails', function () {
+    App::setLocale('de');
+
+    // Create a country with a code that won't be found in ICU data
+    $country = new Country;
+    $country->timestamps = false;
+    $country->code = 'XX';
+    $country->name = 'Unknown Land';
+    $country->phonecode = 0;
+    $country->save();
+
+    $address = Address::factory()->create([
+        'country_id' => $country->id,
+    ]);
+
+    expect($address->country_name)->toBe('Unknown Land');
+});