Navbar with AI chats (#18161)

## Summary
Add Home/Chat tabs and a dedicated threads list in the navigation
drawer.

## Changes
- **Navbar tabs:** Tabs in the drawer to switch between Home and Chat
(with “New chat” button). Shown on desktop when expanded and on mobile
below the workspace selector.
- **Navbar threads list:** New `NavigationDrawerAIChatThreadsList` for
the Chat tab with date groups (Today / Yesterday / Older), thread rows
as `NavigationDrawerItem` (IconComment, title, timestamp). Shared
`useAIChatThreadClick` hook used by navbar and command menu; navbar
passes `resetNavigationStack: true`.
- **NavigationDrawerItem:** New `alwaysShowRightOptions` prop so the
timestamp is always visible (no hover-only).

---------

Co-authored-by: Etienne <45695613+etiennejouan@users.noreply.github.com>
Co-authored-by: Félix Malfait <felix@twenty.com>
Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-front/src/modules/ai/utils/dateGroupKey.ts

@@ -0,0 +1 @@
+export type DateGroupKey = 'today' | 'yesterday' | 'older';