feat: implement Agent Chat Widget for entity pages

TASK_PHASE_AGENT_CHAT_WIDGET_MVP.md completed:

Backend:
- Add /api/v1/agents/{agent_id}/chat-room endpoint
- Add /api/v1/nodes/{node_id}/chat-room endpoint
- Add /api/v1/microdaos/{slug}/chat-room endpoint

Frontend:
- Create AgentChatWidget.tsx floating chat component
- Integrate into /agents/:agentId page
- Integrate into /nodes/:nodeId page
- Integrate into /microdao/:slug page

Ontology rule implemented:
'No page without agents' = ability to directly talk to agents on that page

apps/web/src/app/nodes/[nodeId]/page.tsx

@@ -15,6 +15,7 @@ import {
   NodeStandardComplianceCard
 } from '@/components/node-dashboard';
 import { NodeGuardianCard } from '@/components/nodes/NodeGuardianCard';
+import { AgentChatWidget } from '@/components/chat/AgentChatWidget';
 
 function getNodeLabel(nodeId: string): string {
   if (nodeId.includes('node-1')) return 'НОДА1';
@@ -182,6 +183,9 @@ export default function NodeCabinetPage() {
           </div>
         </div>
       </div>
+      
+      {/* Floating Chat Widget */}
+      <AgentChatWidget contextType="node" contextId={nodeId} />
     );
   }
 
@@ -337,6 +341,9 @@ export default function NodeCabinetPage() {
           <ExternalLink className="w-3 h-3" />
         </Link>
       </div>
+      
+      {/* Floating Chat Widget */}
+      <AgentChatWidget contextType="node" contextId={nodeId} />
     </div>
   );
 }