Fix geocache message notifications for cross-device alerts

- Fixed notification not triggering when adding message from another device
- Now notifies ALL devices (including your own) when near a cache with new message
- Added null checks for messages array to prevent errors
- Notifications work for messages from same user on different devices

This fixes the issue where adding a message from desktop wouldn't
notify your phone even when nearby.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

geocaches.json

@@ -47,6 +47,16 @@
         "author": "Riker",
         "text": "Stupid little cousin ibby dibby...",
         "timestamp": 1767133204544
+      },
+      {
+        "author": "Presley",
+        "text": "BARK! god damnit BARK!",
+        "timestamp": 1767199495387
+      },
+      {
+        "author": "test",
+        "text": "test",
+        "timestamp": 1767199518737
       }
     ],
     "createdAt": 1767127362829,

index.html

@@ -2552,19 +2552,22 @@
                             break;
 
                         case 'geocacheUpdate':
-                            // Another user added or updated a geocache
+                            // Another user or device added or updated a geocache
                             if (data.geocache) {
                                 const existingIndex = geocaches.findIndex(g => g.id === data.geocache.id);
                                 if (existingIndex >= 0) {
-                                    // Check if this is a new message from another user
+                                    // Check if this is a new message
                                     const oldCache = geocaches[existingIndex];
-                                    const newMessagesCount = data.geocache.messages.length - oldCache.messages.length;
+                                    const oldMessageCount = oldCache.messages ? oldCache.messages.length : 0;
+                                    const newMessageCount = data.geocache.messages ? data.geocache.messages.length : 0;
+                                    const newMessagesCount = newMessageCount - oldMessageCount;
 
                                     // Update existing geocache
                                     geocaches[existingIndex] = data.geocache;
 
-                                    // Send notification if new message added by another user and we're nearby
-                                    if (newMessagesCount > 0 && userLocation) {
+                                    // Send notification if new message added and we're nearby
+                                    // This will notify even if it's from your own account on another device
+                                    if (newMessagesCount > 0 && userLocation && pushSubscription) {
                                         const distance = L.latLng(userLocation.lat, userLocation.lng)
                                             .distanceTo(L.latLng(data.geocache.lat, data.geocache.lng));