Add Feedback Buttons on Chat

[MythicalCow]

Description and Rationale for Changes

This feature includes thumbs up and thumbs down buttons on Khoj's chat responses that provide automated feedback. When a thumbs up/down button is clicked, the code sends an email to team@khoj.dev with the following:

• user query
• khoj's response
• whether the sentiment of the user was good or bad.

This is critical in improving Khoj's nondeterministic LLM model for a better user experience.

List of Changes

• new endpoint in api_chat.py (/feedback) that can be used to trigger mail sending).
• thumbs up and thumbs down buttons implemented in chat.html
• new function in routers/email.py to handle feedback email sending via resend
• feedback.html template for a formatted email with the feedback.

Demo Images

[sabaimran]

This is awesome! It'll be super useful being able to collect in-app feedback. Just a few comments, but the structure is great.