v2.4.0 — OIDC login, OpenStreetMap search, account management

Features:
- Single Sign-On (OIDC) — login with Google, Apple, Authentik, Keycloak
- OpenStreetMap place search as free fallback when no Google API key
- Change password in user settings
- Delete own account (with last-admin protection)
- Last login column in admin user management
- SSO badge and provider info in user settings
- Google API key "Recommended" badge in admin panel

Improvements:
- API keys load correctly after page reload
- Validate auto-saves keys before testing
- Time format respects 12h/24h setting everywhere
- Dark mode fixes for popups and backup buttons
- Admin stats: removed photos, 4-column layout
- Profile picture upload button on avatar overlay
- TravelStats duplicate key fix
- Backup panel dark mode support

server/package.json

@@ -1,6 +1,6 @@
 {
   "name": "nomad-server",
-  "version": "2.3.5",
+  "version": "2.4.0",
   "main": "src/index.js",
   "scripts": {
     "start": "node --experimental-sqlite src/index.js",