Add full text search support

[canny]

As a user of the application, I want to have full text search support within the chat interface, so that I can easily find and reference specific conversations or messages without manually scrolling through the chat history. Currently, the implementation only supports searching through titles. The search bar should be prominently displayed at the top of the chat interface, support full text search capabilities, display results in a list format, and highlight the search term within the chat. The functionality should be optimized for performance and designed to fit seamlessly into the existing chat interface, ensuring a clean and user-friendly experience.

https://betterchatgpt.canny.io/admin/board/feature-requests/p/add-full-text-search-support