fix: prevent page hang when device channel queries block

/api/messages and /api/messages/updates called get_channels_cached()
which blocks on device communication when cache is cold (up to 240s).
Now uses DB-cached channels for pkt_payload computation instead.

Frontend loadMessages() now has a 15s timeout with auto-retry
and clears the loading spinner on error instead of leaving it
spinning indefinitely.

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

app/routes/api.py

@@ -371,14 +371,15 @@ def get_messages():
                 )
 
             # Build channel secret lookup for pkt_payload computation
+            # Use DB channels (fast) instead of get_channels_cached() which
+            # can block on device communication when cache is cold
             channel_secrets = {}
-            _, channels_list = get_channels_cached()
-            if channels_list:
-                for ch_info in channels_list:
-                    ch_key = ch_info.get('key', '')
-                    ch_idx = ch_info.get('index')
-                    if ch_key and ch_idx is not None:
-                        channel_secrets[ch_idx] = ch_key
+            db_channels = db.get_channels() if db else []
+            for ch_info in db_channels:
+                ch_key = ch_info.get('secret', ch_info.get('key', ''))
+                ch_idx = ch_info.get('idx', ch_info.get('index'))
+                if ch_key and ch_idx is not None:
+                    channel_secrets[ch_idx] = ch_key
 
             # Convert DB rows to frontend-compatible format
             messages = []
@@ -485,15 +486,15 @@ def get_message_meta(msg_id):
         txt_type = row.get('txt_type', 0)
 
         # Compute pkt_payload if not stored
+        # Use DB channels (fast) to avoid blocking on device communication
         if not pkt_payload and sender_ts:
-            _, channels_list = get_channels_cached()
+            db_channels = db.get_channels() if db else []
             channel_secrets = {}
-            if channels_list:
-                for ch_info in channels_list:
-                    ch_key = ch_info.get('key', '')
-                    ci = ch_info.get('index')
-                    if ch_key and ci is not None:
-                        channel_secrets[ci] = ch_key
+            for ch_info in db_channels:
+                ch_key = ch_info.get('secret', ch_info.get('key', ''))
+                ci = ch_info.get('idx', ch_info.get('index'))
+                if ch_key and ci is not None:
+                    channel_secrets[ci] = ch_key
 
             if ch_idx in channel_secrets:
                 raw_text = None
@@ -1698,17 +1699,17 @@ def get_messages_updates():
         except (json.JSONDecodeError, ValueError):
             last_seen = {}
 
-        # Get list of channels (cached)
-        success_ch, channels = get_channels_cached()
-        if not success_ch:
-            return jsonify({
-                'success': False,
-                'error': 'Failed to get channels'
-            }), 500
+        # Get list of channels from DB (fast) to avoid blocking on device
+        db = _get_db()
+        db_channels = db.get_channels() if db else []
+        # Normalize DB channel format to match expected structure
+        channels = [{'index': ch['idx'], 'name': ch['name']} for ch in db_channels]
+        if not channels:
+            # Fallback: at least include Public channel
+            channels = [{'index': 0, 'name': 'Public'}]
 
         # OPTIMIZATION: Read ALL messages ONCE (no channel filter)
         # Then compute per-channel statistics in memory
-        db = _get_db()
         if db:
             all_messages = db.get_channel_messages(limit=None, days=7)
         else:

app/static/js/app.js

@@ -854,7 +854,12 @@ async function loadMessages() {
             url += '&days=7';
         }
 
-        const response = await fetch(url);
+        // Add timeout to prevent hanging spinner
+        const controller = new AbortController();
+        const timeoutId = setTimeout(() => controller.abort(), 15000);
+
+        const response = await fetch(url, { signal: controller.signal });
+        clearTimeout(timeoutId);
         const data = await response.json();
 
         if (data.success) {
@@ -863,11 +868,31 @@ async function loadMessages() {
             updateLastRefresh();
         } else {
             showNotification('Error loading messages: ' + data.error, 'danger');
+            clearLoadingSpinner();
         }
     } catch (error) {
         console.error('Error loading messages:', error);
         updateStatus('disconnected');
-        showNotification('Failed to load messages', 'danger');
+        clearLoadingSpinner();
+        if (error.name === 'AbortError') {
+            showNotification('Loading messages timed out — retrying...', 'warning');
+            setTimeout(loadMessages, 2000);
+        } else {
+            showNotification('Failed to load messages', 'danger');
+        }
+    }
+}
+
+function clearLoadingSpinner() {
+    const container = document.getElementById('messagesList');
+    if (container && container.querySelector('.spinner-border')) {
+        container.innerHTML = `
+            <div class="empty-state">
+                <i class="bi bi-exclamation-triangle"></i>
+                <p>Could not load messages</p>
+                <small>Will retry automatically</small>
+            </div>
+        `;
     }
 }