NGINX proxy config hostname collision

### Steps To Reproduce

1. Deploy another docker container or stack outside of Bitwarden which has a container named "web"
2. Deploy standard configuration via `./bitwarden.sh start`
3. Attempt to access vault via browser

### Expected Result

Vault login website should appear.

### Actual Result

Browser responds with 502 error page from nginx.

### Screenshots or Videos

_No response_

### Additional Context

Searching the nginx error logs within `bwdata` folder shows

```
[warn] 48#48: *210 upstream server temporarily disabled while connecting to upstream ...
[error] 48#48: *210 connect() failed (111: Connection refused) while connecting to upstream ...
```

Upstream server in the logs is listed with IP address of the other, already running docker container with the name `web` despite that container being in another Docker network.

It seems to be caused by the following line in nginx's `default.conf` file:
```
location / {
proxy_pass http://web:5000/;
...
}
```

I believe this could be remedied by having `bitwarden.sh` generate the file and appending the `bitwarden_internal` network domain to all of the hosts in `default.conf` rather than relying on Docker's DNS system to resolve the correct IP with only the hostname.

ex:
```
location / {
proxy_pass http://web.bitwarden_internal:5000/;
...
}
```

### Build Version

2025.4.1

### Environment

Self-Hosted

### Environment Details

- Operating System: Debian 12 (bookworm)
- Environment: Docker

### Issue Tracking Info

- [x] I understand that work is tracked outside of Github. A PR will be linked to this issue should one be opened to address it, but Bitwarden doesn't use fields like "assigned", "milestone", or "project" to track progress.