Fix API endpoint configuration and domain references

- Change NEXT_PUBLIC_ENTE_ENDPOINT to relative /api for domain flexibility
- Remove runtime JS endpoint replacement (fragile, now unnecessary)
- Fix all domain references to use CLOUDRON_APP_DOMAIN consistently
- Add /ping health check endpoint to Caddy configuration
- Update placeholder server to use dynamic domain

Photos app now working, other apps may need additional fixes.

CloudronManifest.json

@@ -7,7 +7,7 @@
   "contactEmail": "contact@ente.io",
   "tagline": "Open Source End-to-End Encrypted Photos & Authentication",
   "upstreamVersion": "1.0.0",
-  "version": "0.1.62",
+  "version": "0.1.63",
   "healthCheckPath": "/ping",
   "httpPort": 3080,
   "memoryLimit": 1073741824,