fix(perf): polling-only Socket.IO + channels DB fallback on USB timeout

Werkzeug dev server can't upgrade WebSockets, so every io() upgrade attempt
returned HTTP 500 and clients fell into a polling/upgrade reconnect loop —
visible as 10-15s freezes on app load. Force transports: ['polling'] on
/chat, /console and /logs clients; long-poll keeps real-time pushes
working with ~1-2s latency.

When the MeshCore device briefly stalls, get_channel_info() used to block
on the default 30s timeout per slot, so iterating max_channels slots could
take minutes; in practice only Public answered and the rest timed out,
leaving the UI with just one channel. Drop per-call timeout to 3s, raise
TimeoutError to the caller, and have cli.get_channels() break on first
timeout and merge the remaining slots from the channels table in the DB
(which already mirrors device state via upsert_channel).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/static/js/app.js

@@ -403,7 +403,8 @@ function connectChatSocket() {
 
     const wsUrl = window.location.origin;
     chatSocket = io(wsUrl + '/chat', {
-        transports: ['websocket', 'polling'],
+        transports: ['polling'],
+        upgrade: false,
         reconnection: true,
         reconnectionDelay: 2000,
         reconnectionDelayMax: 10000,

app/static/js/console.js

@@ -38,7 +38,8 @@ function connectWebSocket() {
 
     try {
         socket = io(wsUrl + '/console', {
-            transports: ['websocket', 'polling'],
+            transports: ['polling'],
+            upgrade: false,
             reconnection: true,
             reconnectionAttempts: Infinity,
             reconnectionDelay: 1000,

app/static/js/dm.js

@@ -125,7 +125,8 @@ function connectChatSocket() {
 
     const wsUrl = window.location.origin;
     chatSocket = io(wsUrl + '/chat', {
-        transports: ['websocket', 'polling'],
+        transports: ['polling'],
+        upgrade: false,
         reconnection: true,
         reconnectionDelay: 2000,
         reconnectionDelayMax: 10000,

app/static/js/logs.js

@@ -33,7 +33,8 @@
 
     // --- WebSocket ---
     const socket = io('/logs', {
-        transports: ['websocket', 'polling'],
+        transports: ['polling'],
+        upgrade: false,
         reconnection: true,
         reconnectionDelay: 2000,
     });