feat: add bulk client notifications and email enhancements with review fixes (Stories 3.4 & 3.5)

Story 3-4: Bulk client notification scheduling — BulkNotificationController,
BulkActionBar component, checkbox selection on declarations index.

Story 3-5: Email notification enhancement — observer-driven email on
en_attente_client, cache invalidation on ferme, workspace branding on
all email templates, 11 feature tests.

Code review fixes:
- Move bulk-notify route above resource wildcard to prevent shadowing
- Add static $suppressEmail flag to prevent observer double-sending
  when DeclarationMessageController already sends the email
- Fix canBulkNotify logic (was granting workers access)
- Add WorkspaceUserRole check to BulkNotifyRequest::authorize()
- Replace firstOrCreate with explicit invitation lookup that syncs
  client email and handles used/expired invitations correctly
- Watch declarations.data instead of current_page to clear selection
  on filter/sort changes

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

app/Http/Controllers/DeclarationMessageController.php

@@ -15,6 +15,7 @@ use App\Models\Declaration;
 use App\Models\DeclarationInvitation;
 use App\Models\Message;
 use App\Models\Workspace;
+use App\Observers\DeclarationObserver;
 use Carbon\Carbon;
 use Illuminate\Http\RedirectResponse;
 use Illuminate\Http\Request;
@@ -73,6 +74,8 @@ class DeclarationMessageController extends Controller
             $message->update(['metadata' => array_merge($metadata, ['media_ids' => $mediaIds])]);
         }
 
+        // Suppress observer email — this controller sends its own email below
+        DeclarationObserver::$suppressEmail = true;
         $this->updateDeclarationStatusAndConfirmation($declaration, $type, $mediaIds);
 
         $emailSent = $this->sendEmailForMessage($declaration, $invitation, $message, $body, $type);