feat: integrate MCP servers as tools in Chat Agent with function calling

Add MCP tool discovery (auto + manual), tool execution via MCP SDK,
and GenAI function calling loop (Cohere + Generic formats) so the
chat agent can invoke MCP server tools during conversations.

- Add mcp SDK dependency
- New endpoints: discover-tools, update tools
- Modify _call_genai to support tools/tool_results and return (text, tool_calls)
- Tool use loop in chat endpoint (max 5 iterations)
- Frontend: tools management in MCP cards, chat toggle, tools_used display
- Multi-table ADB vector search, enriched embeddings, preview chunks
- Orphaned report cleanup on container restart
- Nginx no-cache headers, searchable dropdowns, editable vector tables

nginx/default.conf

@@ -8,6 +8,9 @@ server {
         root /usr/share/nginx/html;
         index index.html;
         try_files $uri $uri/ /index.html;
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Pragma "no-cache";
+        add_header Expires 0;
     }
 
     location /api/ {