fix: nginx audio streaming - pass Range headers for proper playback

The nginx proxy was stripping Range and If-Range headers, forcing the
browser to buffer entire MP3 files before playback could start.
Added Range header passthrough, disabled proxy_buffering for audio
streaming, and increased read timeout.

frontend/nginx.conf

@@ -4,6 +4,9 @@ server {
     root /usr/share/nginx/html;
     index index.html;
 
+    # Increase proxy buffer sizes for audio streaming
+    client_max_body_size 100M;
+
     location / {
         try_files $uri $uri/ /index.html;
     }
@@ -13,5 +16,14 @@ server {
         proxy_http_version 1.1;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
+
+        # Enable audio streaming with range requests
+        proxy_set_header Range $http_range;
+        proxy_set_header If-Range $http_if_range;
+        proxy_set_header Connection "";
+        proxy_buffering off;
+
+        # Allow large responses (audio files)
+        proxy_read_timeout 300s;
     }
 }