Add locale-based time formatting in the chat panel (#7945)

This commit addresses the issue of time formats displayed in the chat
panel. Previously, the time was always displayed in a 12-hour format,
regardless of the user's locale. The `format_timestamp` function has
been updated to check the system locale and format the time accordingly.


Release Notes:
- Fixed time formatting in the chat panel to be locale based.

Cargo.lock

@@ -2115,6 +2115,7 @@ dependencies = [
  "settings",
  "smallvec",
  "story",
+ "sys-locale",
  "theme",
  "theme_selector",
  "time",