Git ignore LLM text files + move LLM txt generate logic into build command

[FranjoMindek]

Description

We already built LLM txt files before building for deployment, so we could have git ignored them earlier.
In this PR I:

1. Git ignore LLM txt files
2. Move generate-llm-files inside of build, so it's always tied to our build

Contributor Checklist

Make sure to do the following steps if they are applicable to your PR:

• Update e2e tests: If you changed the /template/app, then make sure to do any neccessary updates to /template/e2e-tests also.
• Update demo app: If you changed the /template/app, then make sure to do any neccessary updates to /opensaas-sh/app_diff also. Check /opensaas-sh/README.md for details.
• Update docs: If needed, update the /opensaas-sh/blog/src/content/docs.