feat: Implement AI Router for Dynamic Agent Selection (#15227)

Adds intelligent routing system that automatically selects the best
agent for user queries based on conversation context.

### Changes:
- Added `routerModel` column to workspace table for configurable router
LLM selection
- Implemented `RouterService` with conversation history analysis and
agent matching logic
- Created router settings UI in AI Settings page with model dropdown
- Removed agent-specific thread associations - threads are now
agent-agnostic
- Added real-time routing status notification in chat UI with shimmer
effect
- Removed automatic default assistant agent creation
- Renamed GraphQL operations from agent-specific to generic (e.g.,
`agentChatThreads` → `chatThreads`)

---------

Co-authored-by: Félix Malfait <felix.malfait@gmail.com>
Co-authored-by: Félix Malfait <felix@twenty.com>

packages/twenty-front/src/modules/command-menu/pages/AIChatThreads/components/CommandMenuAIChatThreadsPage.tsx

@@ -1,37 +1,15 @@
 import { AIChatThreadsList } from '@/ai/components/AIChatThreadsList';
-import { currentWorkspaceState } from '@/auth/states/currentWorkspaceState';
 import styled from '@emotion/styled';
-import { useRecoilValue } from 'recoil';
 
 const StyledContainer = styled.div`
   height: 100%;
   width: 100%;
 `;
 
-const StyledEmptyState = styled.div`
-  align-items: center;
-  color: ${({ theme }) => theme.font.color.secondary};
-  display: flex;
-  font-size: ${({ theme }) => theme.font.size.md};
-  height: 100%;
-  justify-content: center;
-`;
-
 export const CommandMenuAIChatThreadsPage = () => {
-  const currentWorkspace = useRecoilValue(currentWorkspaceState);
-  const agentId = currentWorkspace?.defaultAgent?.id;
-
-  if (!agentId) {
-    return (
-      <StyledContainer>
-        <StyledEmptyState>No AI Agent found.</StyledEmptyState>
-      </StyledContainer>
-    );
-  }
-
   return (
     <StyledContainer>
-      <AIChatThreadsList agentId={agentId} />
+      <AIChatThreadsList />
     </StyledContainer>
   );
 };