When using reverse proxy, some dynamic endpoints do not resolve

### Expected Behavior

example.org/user.css - works, status 200
localhost:8188/user.css - works, status 200

### Actual Behavior

example.org/user.css - doesn't work, status 404
localhost:8188/user.css - works, status 200

### Steps to Reproduce

```
server {
listen 80 default_server;
listen [::]:80 default_server;

gzip on;
gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

client_max_body_size 100M;

location / {
proxy_pass http://127.0.0.1:8188;

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;

# WebSocket support
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
}
```

### Debug Logs

```powershell
Checkpoint files will always be loaded safely.
Total VRAM 22693 MB, total RAM 54232 MB
pytorch version: 2.7.0+cu128
Set vram state to: NORMAL_VRAM
Device: cuda:0 NVIDIA L4 : cudaMallocAsync
Using pytorch attention
Python version: 3.12.10 (main, Apr 9 2025, 08:55:05) [GCC 11.4.0]
ComfyUI version: 0.3.38
ComfyUI frontend version: 1.20.7
```

### Other

maybe there is a guideline, how to properly map nginx to dynamic routes without files?