chat panel ++ (#4044)

- Update chat panel with current channel
- Open chat panel for guests
- Open chat when joining a channel with guests
- Some tweaks for chat panels
- Don't lose focus on default panel state
- Make chat prettier (to my eyes at least)
- Fix multiple mentions in one message
- Show a border when scrolled in chat
- Fix re-docking chat panel
- Move settings subscription to dock

[[PR Description]]

Release Notes:

- Opens chat by default when joining a public channel
- Improves chat panel UI

crates/collab/src/db/queries/messages.rs

@@ -256,6 +256,7 @@ impl Database {
                     message_id = result.last_insert_id;
                     let mentioned_user_ids =
                         mentions.iter().map(|m| m.user_id).collect::<HashSet<_>>();
+
                     let mentions = mentions
                         .iter()
                         .filter_map(|mention| {