Refa: refactor prompts into markdown-style structure using Jinja2 (#8667)

### What problem does this PR solve?

Refactor prompts into markdown-style structure using Jinja2.

### Type of change

- [x] Refactoring

rag/prompts/citation_prompt.md

@@ -0,0 +1,46 @@
+## Citation Requirements
+
+- Use a uniform citation format such as [ID:i] [ID:j], where "i" and "j" are document IDs enclosed in square brackets. Separate multiple IDs with spaces (e.g., [ID:0] [ID:1]).
+- Citation markers must be placed at the end of a sentence, separated by a space from the final punctuation (e.g., period, question mark).
+- A maximum of 4 citations are allowed per sentence.
+- DO NOT insert citations if the content is not from retrieved chunks.
+- DO NOT use standalone Document IDs (e.g., #ID#).
+- Citations MUST always follow the [ID:i] format.
+- STRICTLY prohibit the use of strikethrough symbols (e.g., ~~) or any other non-standard formatting syntax.
+- Any violation of the above rules — including incorrect formatting, prohibited styles, or unsupported citations — will result in no citation being added for that sentence.
+
+---
+
+## Example START
+
+<SYSTEM>: Here is the knowledge base:
+
+Document: Elon Musk Breaks Silence on Crypto, Warns Against Dogecoin ...
+URL: https://blockworks.co/news/elon-musk-crypto-dogecoin
+ID: 0
+The Tesla co-founder advised against going all-in on dogecoin, but Elon Musk said it’s still his favorite crypto...
+
+Document: Elon Musk's Dogecoin tweet sparks social media frenzy
+ID: 1
+Musk said he is 'willing to serve' D.O.G.E. – shorthand for Dogecoin.
+
+Document: Causal effect of Elon Musk tweets on Dogecoin price
+ID: 2
+If you think of Dogecoin — the cryptocurrency based on a meme — you can’t help but also think of Elon Musk...
+
+Document: Elon Musk's Tweet Ignites Dogecoin's Future In Public Services
+ID: 3
+The market is heating up after Elon Musk's announcement about Dogecoin. Is this a new era for crypto?...
+
+The above is the knowledge base.
+
+<USER>: What's Elon's view on dogecoin?
+
+<ASSISTANT>:
+Musk has consistently expressed his fondness for Dogecoin, often citing its humor and the inclusion of dogs in its branding. He has referred to it as his favorite cryptocurrency [ID:0] [ID:1].
+
+Recently, Musk has hinted at potential future roles for Dogecoin. His tweets have sparked speculation about Dogecoin's potential integration into public services [ID:3].
+
+Overall, while Musk enjoys Dogecoin and often promotes it, he also warns against over-investing in it, reflecting both his personal amusement and caution regarding its speculative nature.
+
+## Example END