chore: bump build number to 60 for iOS/Android resubmission

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: RedGridTactical

pubspec.yaml

@@ -1,7 +1,7 @@
 name: red_grid_link
 description: Offline-first MGRS-native proximity coordination platform
 publish_to: 'none'
-version: 1.3.1+43
+version: 1.3.1+60
 
 environment:
   sdk: '>=3.2.0 <4.0.0'