Add `second_brain_url` to edit and create tribe endpoints

[tomsmith8]

Task

Add second_brain_url to the following endpoints:

• https://github.com/stakwork/sphinx-relay/blob/a3b3528a2cbe37b910fd72222dc6c2555df50014/src/controllers/chatTribes.ts#L398

• https://github.com/stakwork/sphinx-relay/blob/a3b3528a2cbe37b910fd72222dc6c2555df50014/src/controllers/chats.ts#L268

• Need to support second_brain_url

• Edit or Create new tribe should be able to store second_brain_url

Acceptance Criteria

• [ ] Update the two endpoints to support second_brain_url

[Evanfeenstra]

why not use app_url here?

[tomsmith8]

We want to have a specific second brain icon in Tribes while still allowing a tribe admin to set a non secondbrain URL in Sphinx