Add edit feature enable/disable setting

- Added checkbox in Settings screen to enable/disable edit feature
- Setting stored in app_config.json as 'edit_feature_enabled'
- Edit workflow now validates: player setting, media type, server permission, card auth
- Shows appropriate error message when edit is blocked at any validation step
- Defaults to enabled (true) if not set
- All conditions must be met for edit interface to open

config/app_config.json

@@ -5,5 +5,6 @@
   "quickconnect_key": "8887779",
   "orientation": "Landscape",
   "touch": "True",
-  "max_resolution": "1920x1080"
+  "max_resolution": "1920x1080",
+  "edit_feature_enabled": true
 }