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/en.json

@@ -212,7 +212,44 @@
       "site": { "manage": "Manage site settings" },
       "comment": { "delete": "Delete comments" },
       "upload": { "delete": "Delete uploads" },
-      "tag": { "delete": "Delete tags" }
+      "tag": { "delete": "Delete tags" },
+      "audit": { "view": "View audit log" }
+    },
+    "audit": {
+      "title": "Audit log",
+      "desc": "Record of all moderation and admin actions. Click a name to filter by that user.",
+      "filterAction": "Filter by action",
+      "allActions": "All actions",
+      "filterUser": "Only show actions by {name}",
+      "clearUser": "Clear user filter",
+      "count": "{n} entries",
+      "refresh": "Refresh",
+      "time": "Time",
+      "actor": "User",
+      "action": "Action",
+      "details": "Details",
+      "deletedUser": "deleted user",
+      "empty": "No entries."
+    },
+    "auditActions": {
+      "delete_upload": "Upload deleted",
+      "bulk_delete_uploads": "Uploads bulk-deleted",
+      "delete_comment": "Comment deleted",
+      "remove_tags": "Tags removed",
+      "create_role": "Role created",
+      "delete_role": "Role deleted",
+      "update_role_permissions": "Permissions changed",
+      "assign_role": "Role assigned",
+      "remove_role": "Role revoked",
+      "update_motd": "Announcement changed"
+    },
+    "auditDetails": {
+      "deleteUpload": "{name} by {user}",
+      "bulkDelete": "{n} uploads",
+      "deleteComment": "{user}: {content}",
+      "role": "{role} → {user}",
+      "noChanges": "no changes",
+      "motdCleared": "Announcement removed"
     }
   },
   "palette": {