Update checker

web/public/config.js

@@ -19,4 +19,5 @@ var config = {
   billing_contact: "",
   web_push_public_key: "",
   disallowed_topics: ["docs", "static", "file", "app", "account", "settings", "signup", "login", "v1"],
+  config_hash: "dev", // Placeholder for development; actual value is generated server-side
 };

web/public/static/langs/en.json

@@ -4,6 +4,8 @@
   "common_add": "Add",
   "common_back": "Back",
   "common_copy_to_clipboard": "Copy to clipboard",
+  "common_refresh": "Refresh",
+  "version_update_available": "New ntfy version available. Please refresh the page.",
   "signup_title": "Create a ntfy account",
   "signup_form_username": "Username",
   "signup_form_password": "Password",