Update Nginx configuration and mock mode initialization for improved backend handling

- Modified Nginx configuration to trust the outer reverse proxy's X-Forwarded-Proto header, enhancing protocol handling.
- Updated initMockMode function in mock.ts to use the backend health endpoint for improved error handling and timeout management, ensuring a more robust fallback to mock data when the backend is unreachable.

nginx.conf

@@ -38,7 +38,9 @@ server {
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
-        proxy_set_header X-Forwarded-Proto $scheme;
+        # Trust the outer reverse proxy's X-Forwarded-Proto when present,
+        # otherwise fall back to the connection scheme.
+        proxy_set_header X-Forwarded-Proto $http_x_forwarded_proto;
         proxy_read_timeout 300s;
         proxy_send_timeout 300s;