Curseforge API Issues should not be fatal if pack is already installed

### Enhancement Type

Improve an existing feature

### Describe the enhancement

If an `AUTO_CURSEFORGE` pack is already install, encountering Curseforge API issues (403 / `Access to https://api.curseforge.com is forbidden or rate-limit has been exceeded`) should not block startup of the Minecraft server.

I have had a pack installed for a bit over a week now. Restarted multiple times, everything has been fine. This morning, I scaled down the server to update a server config and now when I start it up I get:

```
[mc-image-helper] 10:06:47.853 ERROR : Invalid parameter provided for 'install-curseforge' command: Access to https://api.curseforge.com is forbidden or rate-limit has been exceeded. Ensure CF_API_KEY is set to a valid API key from https://console.curseforge.com/ or allow rate-limit to reset.
```

I have already tested my API key and everything locally and it appears to work. I think it is just Cloudflare temporarily flagging my IP or something. But still, a simple restart should not take down the whole server if the startup cannot communicate with Curseforge. The pack is already installed. Throw a warning it could not check for updates or something and let it continue.

Start by locating the install-curseforge command and the AUTO_CURSEFORGE startup handling in this Shell-based Docker image. Reproduce a CurseForge API failure when the pack is already installed; done means startup continues with a warning instead of treating the API error as fatal.

Written by the indexing model from the issue text.