Fix hamburger menu visibility in all dashboards

- Removed CSS that was hiding all hamburger menu buttons
- This was preventing the sidebar toggle button from appearing
- Now all dashboards (admin, board, member) have working toggle buttons
- Board dashboard now has same functionality as admin and member views

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

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

assets/scss/main.scss

@@ -948,12 +948,7 @@ $screen-xl: 1280px;
   }
 }
 
-// Remove any hamburger menu
-.v-app-bar__nav-icon,
-.menu-toggle,
-.hamburger-menu {
-  display: none !important;
-}
+// Keep hamburger menu visible - removed the hiding CSS
 
 // Animation classes
 .animated-entrance {