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/ai/utils/mapDBPartToUIMessagePart.ts

@@ -1,14 +1,10 @@
-import {
-  type ReasoningUIPart,
-  type ToolUIPart,
-  type UIMessagePart,
-  type UITool,
-} from 'ai';
+import { type ReasoningUIPart, type ToolUIPart } from 'ai';
+import { type ExtendedUIMessagePart } from 'twenty-shared/ai';
 import { type AgentChatMessagePart } from '~/generated/graphql';
 
 export const mapDBPartToUIMessagePart = (
   part: AgentChatMessagePart,
-): UIMessagePart<never, Record<string, UITool>> => {
+): ExtendedUIMessagePart => {
   switch (part.type) {
     case 'text':
       return {
@@ -49,6 +45,14 @@ export const mapDBPartToUIMessagePart = (
       return {
         type: 'step-start',
       };
+    case 'data-routing-status':
+      return {
+        type: part.type,
+        data: {
+          text: part.textContent!,
+          state: part.state!,
+        },
+      };
     default:
       {
         if (part.type.includes('tool-') === true) {