fix: close release preflight gaps

Route public health checks to the API, backfill and synchronize job opportunities, stabilize SPA smoke tests, and document operator-only production steps.

job-tracker-ui/nginx.conf

@@ -14,6 +14,16 @@ server {
     try_files $uri /index.html;
   }
 
+  location = /health {
+    proxy_pass http://backend:8080/health;
+    proxy_http_version 1.1;
+
+    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;
+  }
+
   location /api/ {
     proxy_pass http://backend:8080;
     proxy_http_version 1.1;