feat(audit): admin audit log

Audit log
- Add audit_log table (migration + schema) with index on created_at.
- Add auditLog service (writeAudit, getClientIp) and record events for backups
  (create, restore, upload-restore, delete, auto-settings), admin actions
  (users, OIDC, invites, system update, demo baseline, bag tracking, packing
  template delete, addons), and auth (app settings, MFA enable/disable).
- Add GET /api/admin/audit-log with pagination; fix invite insert row id lookup.
- Add AuditLogPanel and Admin tab; adminApi.auditLog.
- Add admin.tabs.audit and admin.audit.* strings in all locale files.
Note: Rebase feature branches so new DB migrations stay after existing ones
  (e.g. file_links) when merging upstream.

client/src/pages/AdminPage.tsx

@@ -13,6 +13,7 @@ import BackupPanel from '../components/Admin/BackupPanel'
 import GitHubPanel from '../components/Admin/GitHubPanel'
 import AddonManager from '../components/Admin/AddonManager'
 import PackingTemplateManager from '../components/Admin/PackingTemplateManager'
+import AuditLogPanel from '../components/Admin/AuditLogPanel'
 import { Users, Map, Briefcase, Shield, Trash2, Edit2, Camera, FileText, Eye, EyeOff, Save, CheckCircle, XCircle, Loader2, UserPlus, ArrowUpCircle, ExternalLink, Download, AlertTriangle, RefreshCw, GitBranch, Sun, Link2, Copy, Plus } from 'lucide-react'
 import CustomSelect from '../components/shared/CustomSelect'
 
@@ -61,6 +62,7 @@ export default function AdminPage(): React.ReactElement {
     { id: 'addons', label: t('admin.tabs.addons') },
     { id: 'settings', label: t('admin.tabs.settings') },
     { id: 'backup', label: t('admin.tabs.backup') },
+    { id: 'audit', label: t('admin.tabs.audit') },
     { id: 'github', label: t('admin.tabs.github') },
   ]
 
@@ -923,6 +925,8 @@ export default function AdminPage(): React.ReactElement {
 
           {activeTab === 'backup' && <BackupPanel />}
 
+          {activeTab === 'audit' && <AuditLogPanel />}
+
           {activeTab === 'github' && <GitHubPanel />}
         </div>
       </div>