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-server/src/engine/metadata-modules/agent/agent.module.ts

@@ -15,6 +15,7 @@ import { UserWorkspaceEntity } from 'src/engine/core-modules/user-workspace/user
 import { UserWorkspaceModule } from 'src/engine/core-modules/user-workspace/user-workspace.module';
 import { AgentRoleModule } from 'src/engine/metadata-modules/agent-role/agent-role.module';
 import { AgentChatController } from 'src/engine/metadata-modules/agent/agent-chat.controller';
+import { AiRouterModule } from 'src/engine/metadata-modules/ai-router/ai-router.module';
 import { ObjectMetadataModule } from 'src/engine/metadata-modules/object-metadata/object-metadata.module';
 import { PermissionsModule } from 'src/engine/metadata-modules/permissions/permissions.module';
 import { RoleTargetsEntity } from 'src/engine/metadata-modules/role/role-targets.entity';
@@ -66,6 +67,7 @@ import { AgentActorContextService } from './services/agent-actor-context.service
     FileModule,
     ObjectMetadataModule,
     PermissionsModule,
+    AiRouterModule,
     WorkspacePermissionsCacheModule,
     WorkspaceCacheStorageModule,
     TokenModule,