[AI] Add thread actions, filters, and archive support (#20068)

## PR Description

### Summary
- Add AI chat thread actions: rename, archive (soft-delete via
`deletedAt`), and hard-delete with confirmation.
- Add chat thread filtering by status (active/archived/all), group-by
mode, and last activity.
- Rework drawer/side-panel thread lists to share thread sections, item
menus, archive icons, and empty-state behavior.
- Extend server chat thread model/API with `deletedAt`, mutations,
broadcasts, and archive-aware stream guards.

### Decisions
- Two-stage lifecycle: Archive sets `deletedAt` (soft); Delete is a
separate action on archived threads that hard-deletes the row. Aligns
with Twenty's soft-delete convention (Felix's suggestion).
- `lastMessageAt` is derived from `MAX(agentMessage.createdAt)` on read,
not stored. List query does inline aggregation for sort; `@ResolveField`
covers single-thread / mutation paths so the schema contract is honest
everywhere. Matches `timeline-messaging.service.ts` precedent and the
existing `totalInputCredits` / `totalOutputCredits` `@ResolveField`
pattern in the same resolver.
- Replaced auto-CRUD `chatThreads` (cursor-paginated Connection) with a
custom `[AgentChatThreadDTO!]` resolver. Frontend metadata-store treats
threads as a flat collection and filters/sorts client-side, so cursor
pagination was performative.
- Sending in an archived chat unarchives it optimistically on the client
and authoritatively on the server.
- Grouping and last-activity filtering use `lastMessageAt ?? updatedAt`
so archive/rename don't bump threads in the list.
- Kept metadata-store core API unchanged; AI chat uses the same local
cast pattern already used by other metadata-store partial updates.


https://github.com/user-attachments/assets/1b179b7b-1a2a-4a7a-aa0a-c88f6f051a87

packages/twenty-front/src/modules/ui/navigation/navigation-drawer/components/NavigationDrawerItem.tsx

@@ -92,15 +92,15 @@ const StyledItem = styled.button<StyledItemProps>`
   border-radius: ${themeCssVariables.border.radius.sm};
   box-sizing: border-box;
   color: ${({ active, isSoon, variant }) => {
+    if (variant === 'tertiary') {
+      return themeCssVariables.font.color.tertiary;
+    }
     if (active === true) {
       return themeCssVariables.font.color.primary;
     }
     if (isSoon) {
       return themeCssVariables.font.color.light;
     }
-    if (variant === 'tertiary') {
-      return themeCssVariables.font.color.tertiary;
-    }
     return themeCssVariables.font.color.secondary;
   }};
   cursor: ${({ isSoon, isDragging }) =>
@@ -129,7 +129,10 @@ const StyledItem = styled.button<StyledItemProps>`
 
   &:hover {
     background: ${themeCssVariables.background.transparent.light};
-    color: ${themeCssVariables.font.color.primary};
+    color: ${({ variant }) =>
+      variant === 'tertiary'
+        ? themeCssVariables.font.color.tertiary
+        : themeCssVariables.font.color.primary};
   }
 
   &:hover .keyboard-shortcuts {