feat: notification system via Mercure for scraping events

- NotificationInterface: add sendInfo() and sendWarning() levels
- SymfonyNotification: implement new levels (publishes to 'notifications' topic)
- ChapterScrapingStarted: carry mangaTitle + chapterNumber, now dispatched
- ScrapeChapterHandler: dispatch ChapterScrapingStarted before scraping loop
- ScrapingEventSubscriber: wire NotificationInterface for started/scraped/failed events
- useMercureNotifications: new global Vue composable subscribing to 'notifications' topic
- App.vue: mount useMercureNotifications() at app root
- SendTestNotificationCommand: `app:notify:test --type --message` for dev/prod testing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/Domain/Shared/Infrastructure/Service/SymfonyNotification.php

@@ -17,18 +17,22 @@ readonly class SymfonyNotification implements NotificationInterface
 
     public function sendSuccess(string $message): void
     {
-        $this->sendUpdate([
-            'status' => 'success',
-            'message' => $message
-        ]);
+        $this->sendUpdate(['status' => 'success', 'message' => $message]);
     }
 
     public function sendError(string $message): void
     {
-        $this->sendUpdate([
-            'status' => 'error',
-            'message' => $message
-        ]);
+        $this->sendUpdate(['status' => 'error', 'message' => $message]);
+    }
+
+    public function sendInfo(string $message): void
+    {
+        $this->sendUpdate(['status' => 'info', 'message' => $message]);
+    }
+
+    public function sendWarning(string $message): void
+    {
+        $this->sendUpdate(['status' => 'warning', 'message' => $message]);
     }
 
     public function sendUpdate(array $data): void