DX-982: Adding Chat Feature to Qstash

[CahidArda]

Adding chat feature to Qstash

Adding types for chat requests and responses like in here.

Todo:

• [x] Pass linter
• [x] Typesafety for mistral system prompt

Dependencies: Only adding ai. It's not used in the code. It's only for converting the stream to text for testing.

[linear[bot]]

DX-982 Adding Chat Namespace to Qstash