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>

routes/web.php

@@ -14,6 +14,9 @@ Route::middleware(['auth', 'verified'])->group(function () {
 
     Route::middleware('workspace')->group(function () {
         Route::resource('clients', \App\Http\Controllers\ClientController::class);
+        Route::post('declarations/bulk-notify', [\App\Http\Controllers\BulkNotificationController::class, 'store'])
+            ->middleware('throttle:5,1')
+            ->name('declarations.bulk-notify');
         Route::resource('declarations', \App\Http\Controllers\DeclarationController::class);
         Route::post('declarations/{declaration}/messages', [\App\Http\Controllers\DeclarationMessageController::class, 'store'])
             ->name('declarations.messages.store');