Chat hotkey suggestions

While in the chat window it'd be nice to have the following hotkeys:

- Control + f to switch to "Jump to chat" search bar
- Option + ↑/↓ to move vertically among entries in the sidebar: teams, channels, and private chats

Start by locating the chat window's keyboard handling and the sidebar entries for teams, channels, and private chats. Check how shortcuts are supported on each desktop platform, then verify that Control+f focuses the "Jump to chat" search bar and Option+Up/Down moves through sidebar entries.

Written by the indexing model from the issue text.