Harden frontend assets: disable source maps, add JS obfuscation, env var config

- Disable source maps in production builds (vite.config.ts: sourcemap: false)
- Add vite-plugin-obfuscator for JS obfuscation (hex identifiers, base64 string encoding)
- Move OIDC config behind VITE_* env vars with dev fallbacks (auth/config.ts)
- Add server_tokens off to nginx.conf to stop advertising nginx version
- Add type declaration for vite-plugin-obfuscator

frontend/src/constants/index.ts

@@ -17,6 +17,7 @@ export const API_ENDPOINTS = {
 
 // Map configuration
 export const MAP_CONFIG = {
+  // Dev fallback token — production builds must set VITE_MAPBOX_TOKEN
   MAPBOX_TOKEN: import.meta.env.VITE_MAPBOX_TOKEN || 'pk.eyJ1IjoiZGktdG8iLCJhIjoiY2o0bnBoYXcxMW1mNzJ3bDhmc2xiNWttaiJ9.ZccatVk_4shzoAsEUXXecA',
   DEFAULT_CENTER: [13.38032, 49.994210] as [number, number],
   DEFAULT_ZOOM: 5,