fix: add tls_ca, tls_cert, tls_key to frontend Node interface

NodeContext.tsx was missing the three TLS fields that were already
present on the backend Node type, causing TS2339 build errors in
NodeManager.tsx.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/context/NodeContext.tsx

@@ -15,6 +15,9 @@ export interface Node {
   ssh_user?: string;
   ssh_password?: string;
   ssh_key?: string;
+  tls_ca?: string;
+  tls_cert?: string;
+  tls_key?: string;
 }
 
 interface NodeContextType {