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/Requests/BulkNotifyRequest.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Http\Requests;
+
+use App\Enums\WorkspaceUserRole;
+use Illuminate\Foundation\Http\FormRequest;
+
+class BulkNotifyRequest extends FormRequest
+{
+    /**
+     * Determine if the user is authorized to make this request.
+     */
+    public function authorize(): bool
+    {
+        $user = $this->user();
+
+        if (! $user) {
+            return false;
+        }
+
+        $workspaceUser = $user->currentWorkspaceUser();
+
+        return ! $workspaceUser->role->is(WorkspaceUserRole::Worker);
+    }
+
+    /**
+     * Get the validation rules that apply to the request.
+     *
+     * @return array<string, \Illuminate\Contracts\Validation\ValidationRule|array<mixed>|string>
+     */
+    public function rules(): array
+    {
+        return [
+            'declaration_ids' => ['required', 'array', 'min:1', 'max:100'],
+            'declaration_ids.*' => ['integer'],
+        ];
+    }
+}