feat(D): Phase D — Undo/Restore komplett implementiert

- D-GEN: RestoreRegistry mit RestoreConfig (model_class, restore_permission, excluded_fields, special_handler)
- D-HOOK: history_hooks.py mit register_history_hooks() für after_create/update/delete
- D-CORE: Company create+update record_history in companies.py
- D-PLUG: Task/Calendar/DMS record_history in services/routes
- D-SOFT: Alle registrierten Entitäten haben deleted_at + un-delete via Registry
- D-MAIL: Mail special_handler (IMAP Trash-Move, Folder-Verify) + record_history in delete/move
- D-TRASH: GET /entity-history/trash (filterbar, paginiert) + Frontend Trash.tsx
- D-TOAST: UndoToast.tsx (5s Auto-Dismiss, useUndoToast Hook)
- D-HIST-UI: HistoryPanel.tsx (Timeline, Diff-View, Restore-Button)
- D-BULK: POST /entity-history/bulk-restore mit partial_success Semantik
- D-RET: POST /entity-history/retention/archive (GDPR hard-delete >90 Tage)
- D-TEST: 26 Tests in test_restore_registry.py, alle grün
- D-DOC: test-strategy.md + security_kernel.md aktualisiert

Backend: 10 Dateien, Frontend: 7 Dateien, Tests: 1 Datei, Docs: 3 Dateien
26/26 Tests passed, TSC 0 errors, App import 492 routes

app/plugins/builtins/mail/routes.py

@@ -1643,6 +1643,18 @@ async def delete_mail(
     account = await _get_account(db, mail.account_id, tenant_id, user_id, is_system_admin=is_system_admin)
     await _check_delegate_access(db, account, user_id, "delete")
 
+    # Capture snapshot before delete for history/restore (D-MAIL)
+    from app.services.entity_history_service import record_history
+    mail_snapshot = {
+        "id": str(mail.id),
+        "folder_id": str(mail.folder_id) if mail.folder_id else None,
+        "subject": mail.subject if hasattr(mail, "subject") else None,
+        "account_id": str(mail.account_id),
+        "is_read": mail.is_read if hasattr(mail, "is_read") else None,
+        "is_flagged": mail.is_flagged if hasattr(mail, "is_flagged") else None,
+    }
+    await record_history(db, tenant_id, user_id, "mail", mail.id, "delete", snapshot_before=mail_snapshot)
+
     # Find the Trash folder for this account
     trash_folder = None
     all_folders = (
@@ -1757,9 +1769,22 @@ async def move_mail(
     ).scalar_one_or_none()
     if not target_folder:
         raise HTTPException(404, detail={"detail": "Target folder not found", "code": "not_found"})
+    # Capture snapshot before move (D-MAIL)
+    from app.services.entity_history_service import record_history
+    snapshot_before = {
+        "id": str(mail.id),
+        "folder_id": str(mail.folder_id) if mail.folder_id else None,
+        "subject": mail.subject if hasattr(mail, "subject") else None,
+        "is_read": mail.is_read if hasattr(mail, "is_read") else None,
+        "is_flagged": mail.is_flagged if hasattr(mail, "is_flagged") else None,
+    }
     # Update mail.folder_id
     mail.folder_id = target_f_id
     await db.flush()
+    snapshot_after = {**snapshot_before, "folder_id": str(target_f_id)}
+    changes = {"folder_id": {"old": snapshot_before.get("folder_id"), "new": str(target_f_id)}}
+    await record_history(db, tenant_id, user_id, "mail", mail.id, "update",
+                         snapshot_before=snapshot_before, snapshot_after=snapshot_after, changes=changes)
     # IMAP move: queue for retry if it fails
     try:
         await mail_services.imap_move_mail(db, m_id, target_f_id, tenant_id)