Add public events page, event detail route, copy URL button, organizer events list

- Add /evenements public page with Meilisearch search, KnpPaginator (12/page), event cards grid
- Add /evenement/{orgaSlug}/{id}-{eventSlug} public route with slug redirect
- Add Event::getSlug() method
- Update homepage stats with real event count
- Update organizer detail page to list their public events
- Update navbar: link Evenements to /evenements with active state
- Add copy URL button on edit event page (visible only when online)
- Add initCopyUrl() in app.js with clipboard API

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/Entity/EventTest.php

@@ -144,6 +144,19 @@ class EventTest extends TestCase
         self::assertSame($event, $result);
     }
 
+    public function testGetSlug(): void
+    {
+        $event = new Event();
+        $event->setTitle('Brocante de printemps 2026');
+        self::assertSame('brocante-de-printemps-2026', $event->getSlug());
+    }
+
+    public function testGetSlugEmpty(): void
+    {
+        $event = new Event();
+        self::assertSame('evenement', $event->getSlug());
+    }
+
     public function testIsSecretDefaultFalse(): void
     {
         $event = new Event();