feat(rag): Implement script-based document uploading

[erikleblanc]

Create a CLI or Python script that calls the new RAG endpoint (#37) to upload text files for indexing. This allows devs to keep the knowledge base updated.

Wait for

#37 (Indexing API).

Next Steps

#39 (Document the workflow).
#40 (Usage guide with step-by-step instructions).

Checklist

• Script can read local text/pdf files.
• POST them to RAG endpoint successfully.
• Error handling for invalid file types or big files.