Feature/multi rag

[zzen0008]

Extend RAG Contexts to Support PDF and WebSearch Simultaneously

Enhanced the RAG context to support both PDF and web search in parallel. Here are the main changes made:

1. Refactor buildPrompt function: Refactored the buildPrompt function and its implementations to support multiple RAG contexts. Specifically adjusted for web search and PDF chat. Accommodates more than one RAG context.

2. Update conversation endpoints: Updated the conversation endpoints in the server to match the refactored buildPrompt function, replacing ragContext with ragContexts. This ensures that the conversation can handle these two types of contexts.

3. Update rag.ts: Updated rag.ts to export webSearch and pdfChat separately from the RAGs namespace. This makes their usage in the code more explicit.

4. Alter Message type: Altered the Message type to include ragContexts which will hold the webSearch and pdfChat contexts.

5. Adapt POST method: Adapted the POST method in routes/conversation/[id]/+server.ts to make use of the new ragContexts. Consequently, whichever context is retrieved, it is set in the relevant field of the last message in the conversation.

[itaybar]

I realy appreciate this PR, I think this is a great one. I Wrote one comment that I think will be realy major to make this feature WAY more generic and scaleable