Update media-server: Add backdrop click-to-close for dialogs

- Add dirty state tracking for script and callback forms
- Add backdrop click event listeners to detect clicks outside dialogs
- Add unsaved changes confirmation when closing dialogs with modifications
- Reset dirty state when opening dialogs or after successful save
- Add localized confirmation messages (EN/RU) for unsaved changes

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

media_server/static/locales/en.json

@@ -64,6 +64,7 @@
   "scripts.msg.load_failed": "Failed to load script details",
   "scripts.msg.list_failed": "Failed to load scripts",
   "scripts.confirm.delete": "Are you sure you want to delete the script \"{name}\"?",
+  "scripts.confirm.unsaved": "You have unsaved changes. Are you sure you want to discard them?",
   "callbacks.management": "Callback Management",
   "callbacks.description": "Callbacks are scripts triggered automatically by media control events (play, pause, stop, etc.)",
   "callbacks.add": "Add",
@@ -105,5 +106,6 @@
   "callbacks.msg.not_found": "Callback not found",
   "callbacks.msg.load_failed": "Failed to load callback details",
   "callbacks.msg.list_failed": "Failed to load callbacks",
-  "callbacks.confirm.delete": "Are you sure you want to delete the callback \"{name}\"?"
+  "callbacks.confirm.delete": "Are you sure you want to delete the callback \"{name}\"?",
+  "callbacks.confirm.unsaved": "You have unsaved changes. Are you sure you want to discard them?"
 }