Add browser and unit test suite with Pest + Playwright

Add comprehensive test coverage for core site features (content,
navigation, language, FAQ, news, petition, newsletter) using Pest
browser tests and unit tests for custom plugins. Includes test
infrastructure (Containerfile.test, compose.test.yaml), test
documentation, and test files covering petition form logic, CSV
handling, translation, date formatting, rate limiting, and map data
building.

tests/Browser/FaqTest.php

@@ -0,0 +1,26 @@
+<?php
+
+it('FAQ listing page loads', function () {
+    $this->visit(BASE_URL . '/faq')
+        ->assertSee('Ofte stilte spørsmål');
+});
+
+it('FAQ listing shows question items', function () {
+    $this->visit(BASE_URL . '/faq')
+        ->assertSee('medisinsk cannabis');
+});
+
+it('individual FAQ article loads', function () {
+    $this->visit(BASE_URL . '/faq/Hva-er-MC')
+        ->assertSourceHas('<main');
+});
+
+it('individual FAQ article shows content', function () {
+    $this->visit(BASE_URL . '/faq/Hva-er-MC')
+        ->assertSee('medisinsk cannabis');
+});
+
+it('FAQ article about driving license loads', function () {
+    $this->visit(BASE_URL . '/faq/forerkort')
+        ->assertSourceHas('<main');
+});