fix: resolve permission toggle persistence, nudge terminology, and bulk action bugs (Bugs #2-5)

- Fix togglePermission() to always include all permission keys with false defaults
- Add migration to backfill null/empty Manager permissions with config defaults
- Rename nudge UI text from "Relance" to "Notification"/"Notifier" across 8 files
- Fix select-all checkbox and show checkboxes on all declaration rows
- Remove en_attente_client status restriction from BulkNotificationController

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

app/Mail/NudgeNotificationMail.php

@@ -22,7 +22,7 @@ class NudgeNotificationMail extends Mailable
     public function envelope(): Envelope
     {
         return new Envelope(
-            subject: 'Relance - '.($this->declaration->title ?? 'Sans titre'),
+            subject: 'Notification - '.($this->declaration->title ?? 'Sans titre'),
         );
     }