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/Observers/DeclarationObserver.php

@@ -3,11 +3,21 @@
 namespace App\Observers;
 
 use App\Enums\DeclarationStatus;
+use App\Mail\DeclarationFileRequestMail;
 use App\Models\Declaration;
+use Illuminate\Support\Facades\Cache;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Mail;
 use Illuminate\Validation\ValidationException;
 
 class DeclarationObserver
 {
+    /**
+     * When true, the observer skips sending the client email on en_attente_client.
+     * Set this before updating status when the caller already sends the email.
+     */
+    public static bool $suppressEmail = false;
+
     /**
      * Handle the Declaration "updating" event.
      *
@@ -39,4 +49,95 @@ class DeclarationObserver
             $declaration->archived_at = now();
         }
     }
+
+    /**
+     * Handle the Declaration "updated" event.
+     *
+     * Dispatches side effects on status transitions:
+     * - en_attente_client: queues client email via DeclarationFileRequestMail
+     * - ferme: invalidates dashboard cache for all workspace users
+     */
+    public function updated(Declaration $declaration): void
+    {
+        if (! $declaration->wasChanged('status')) {
+            return;
+        }
+
+        $newStatus = $declaration->status instanceof DeclarationStatus
+            ? $declaration->status->value
+            : (string) $declaration->status;
+
+        if ($newStatus === DeclarationStatus::EnAttenteClient && ! static::$suppressEmail) {
+            $this->sendClientFileRequestEmail($declaration);
+        }
+
+        // Reset suppression flag after each update
+        static::$suppressEmail = false;
+
+        if ($newStatus === DeclarationStatus::Ferme) {
+            $this->invalidateDashboardCache($declaration);
+        }
+    }
+
+    private function sendClientFileRequestEmail(Declaration $declaration): void
+    {
+        $declaration->loadMissing('client');
+        $client = $declaration->client;
+
+        if (! $client || ! $client->contact_email) {
+            return;
+        }
+
+        $mailJob = DB::transaction(function () use ($declaration, $client) {
+            $invitation = $declaration->invitations()
+                ->whereNull('used_at')
+                ->latest()
+                ->first();
+
+            if ($invitation && $invitation->isValid()) {
+                // Reuse valid unused invitation, but sync email with current client
+                if ($invitation->email !== $client->contact_email) {
+                    $invitation->update(['email' => $client->contact_email]);
+                    $invitation->refresh();
+                }
+            } elseif ($invitation && ! $invitation->isValid()) {
+                // Expired but unused — renew it
+                $invitation->update([
+                    'email' => $client->contact_email,
+                    'expires_at' => now()->addDays(30),
+                ]);
+                $invitation->refresh();
+            } else {
+                // No unused invitation exists (all used or none) — create fresh
+                $invitation = $declaration->invitations()->create([
+                    'email' => $client->contact_email,
+                    'expires_at' => now()->addDays(30),
+                ]);
+            }
+
+            $body = 'Nous vous invitons à déposer les documents complémentaires pour votre déclaration "'
+                . $declaration->title . '".';
+
+            return [
+                'email' => $client->contact_email,
+                'mailable' => new DeclarationFileRequestMail($declaration, $invitation, $body),
+            ];
+        });
+
+        Mail::to($mailJob['email'])->queue($mailJob['mailable']);
+    }
+
+    private function invalidateDashboardCache(Declaration $declaration): void
+    {
+        $declaration->loadMissing('workspace.users');
+        $workspace = $declaration->workspace;
+
+        if (! $workspace) {
+            return;
+        }
+
+        $workspace->users->each(function ($user) use ($workspace) {
+            Cache::forget("dashboard:{$workspace->id}:{$user->id}");
+        });
+    }
 }