feat(server): add health api endpoint for increased observability (#3264)

## Description:

Adds an additional API endpoint to the server for health, using the
master lobby service as the health metric. The master lobby service is
considered healthy if the lobby service has started (i.e. it had enough
ready workers to start), and the current amount of ready workers is more
than half of the desired number.

This means that we won't show as healthy until all the workers start,
and then we will continue to show as healthy even if a few workers
crash, as long as at least more than half are still running. Any less
than that, and the service becomes unhealthy.

This also is set to "no cache" in the nginx config. This is to ensure
that any checks of the server health show the true value, and cannot
show false/stale data served by nginx, cloudflare, or anything else.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

jish

nginx.conf

@@ -120,6 +120,25 @@ server {
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
     }
+
+    # /api/health endpoint - No caching, always hit the backend
+    location = /api/health {
+        proxy_pass http://127.0.0.1:3000;
+        proxy_http_version 1.1;
+
+        # Cache configuration - No caching for health checks
+        proxy_cache off;
+        add_header X-Cache-Status "BYPASS";
+        add_header Cache-Control "no-store, no-cache, must-revalidate, proxy-revalidate";
+        add_header Pragma "no-cache";
+        add_header Expires "0";
+
+        # Standard proxy headers
+        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;
+    }
     
     # /commit.txt endpoint - Cache for 5 seconds
     location = /commit.txt {
@@ -250,4 +269,4 @@ server {
         proxy_set_header X-Forwarded-Proto $scheme;
     }
     
-}
+}