fix: cluster edge type and label now persisted on connect

- canvasStore.onConnect was hardcoding type=ethernet and ignoring edgeData fields (type, label, color, etc.)
- EdgeModal had no key, so useState was not reset between connections — initial prop ignored
- Added key based on source/target/handles so modal re-mounts for each new connection

frontend/src/App.tsx

@@ -261,6 +261,7 @@ export default function App() {
         />
 
         <EdgeModal
+          key={pendingConnection ? `${pendingConnection.source}-${pendingConnection.sourceHandle}-${pendingConnection.target}-${pendingConnection.targetHandle}` : 'conn-idle'}
           open={!!pendingConnection}
           onClose={() => setPendingConnection(null)}
           onSubmit={handleEdgeConfirm}