fix(websocket): listen for echo events to update message metadata in real-time

The backend already emits 'echo' SocketIO events when RX_LOG_DATA arrives
with route/path data, but the frontend wasn't listening. Now the frontend
handles echo events with a debounced loadMessages() refresh (2s delay) to
pick up computed pkt_payload, analyzer_url, hops, and route info.

This fixes messages appearing without metadata until manual page refresh.

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

app/static/js/app.js

@@ -422,6 +422,19 @@ function connectChatSocket() {
         }
     });
 
+    // Real-time echo data — refresh messages to pick up route/analyzer metadata
+    let echoRefreshTimer = null;
+    chatSocket.on('echo', (data) => {
+        if (currentArchiveDate) return;  // Don't refresh archive view
+        if (data.direction !== 'incoming') return;  // Only care about incoming echoes
+        // Debounce: wait for echoes to settle, then refresh once
+        if (echoRefreshTimer) clearTimeout(echoRefreshTimer);
+        echoRefreshTimer = setTimeout(() => {
+            echoRefreshTimer = null;
+            loadMessages();
+        }, 2000);
+    });
+
     // Real-time device status
     chatSocket.on('device_status', (data) => {
         const statusEl = document.getElementById('connectionStatus');