Add audit log for moderation and admin actions

New audit_log table records actor, action, target and a JSON snapshot
of the details, so entries stay readable after the target is deleted;
the actor is set to NULL when the user is removed. logAudit() is called
from upload delete (single and bulk), comment delete, tag removal, role
create/delete, role permission changes, role assign/revoke and MOTD
updates. Logging failures only warn and never fail the action itself.

The admin page gets an audit card behind the new audit.view permission
with action filter, click-to-filter by user, readable summaries per
action and server-side pagination. Action catalog lives in
shared/utils/audit.ts, labels under admin.auditActions (de/en).

Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

i18n/locales/de.json

@@ -212,7 +212,44 @@
       "site": { "manage": "Seiten-Einstellungen verwalten" },
       "comment": { "delete": "Kommentare löschen" },
       "upload": { "delete": "Uploads löschen" },
-      "tag": { "delete": "Tags löschen" }
+      "tag": { "delete": "Tags löschen" },
+      "audit": { "view": "Audit-Log einsehen" }
+    },
+    "audit": {
+      "title": "Audit-Log",
+      "desc": "Protokoll aller Moderations- und Admin-Aktionen. Klick auf einen Namen filtert nach diesem Nutzer.",
+      "filterAction": "Nach Aktion filtern",
+      "allActions": "Alle Aktionen",
+      "filterUser": "Nur Aktionen von {name} anzeigen",
+      "clearUser": "Nutzerfilter entfernen",
+      "count": "{n} Einträge",
+      "refresh": "Aktualisieren",
+      "time": "Zeit",
+      "actor": "Nutzer",
+      "action": "Aktion",
+      "details": "Details",
+      "deletedUser": "gelöschter Nutzer",
+      "empty": "Keine Einträge."
+    },
+    "auditActions": {
+      "delete_upload": "Upload gelöscht",
+      "bulk_delete_uploads": "Uploads gesammelt gelöscht",
+      "delete_comment": "Kommentar gelöscht",
+      "remove_tags": "Tags entfernt",
+      "create_role": "Rolle angelegt",
+      "delete_role": "Rolle gelöscht",
+      "update_role_permissions": "Berechtigungen geändert",
+      "assign_role": "Rolle zugewiesen",
+      "remove_role": "Rolle entzogen",
+      "update_motd": "Ansage geändert"
+    },
+    "auditDetails": {
+      "deleteUpload": "{name} von {user}",
+      "bulkDelete": "{n} Uploads",
+      "deleteComment": "{user}: {content}",
+      "role": "{role} → {user}",
+      "noChanges": "keine Änderungen",
+      "motdCleared": "Ansage entfernt"
     }
   },
   "palette": {