Simplify web push UX and updates

- Use a single endpoint
- Use a declarative web push sync hook. This thus handles all edge cases
  that had to be manually handled before: logout, login, account sync,
  etc.
- Simplify UX: browser notifications are always enabled (unless denied),
  web push toggle only shows up if permissions are already granted.

web/public/static/langs/en.json

@@ -52,6 +52,8 @@
   "nav_button_connecting": "connecting",
   "nav_upgrade_banner_label": "Upgrade to ntfy Pro",
   "nav_upgrade_banner_description": "Reserve topics, more messages & emails, and larger attachments",
+  "alert_notification_permission_required_title": "Permission required",
+  "alert_notification_permission_required_description": "Please click here to enable notifications",
   "alert_notification_permission_denied_title": "Notifications are blocked",
   "alert_notification_permission_denied_description": "Please re-enable them in your browser and refresh the page to receive notifications",
   "alert_notification_ios_install_required_title": "iOS Install Required",
@@ -94,9 +96,7 @@
   "notifications_example": "Example",
   "notifications_more_details": "For more information, check out the <websiteLink>website</websiteLink> or <docsLink>documentation</docsLink>.",
   "notification_toggle_unmute": "Unmute",
-  "notification_toggle_sound": "Sound only",
-  "notification_toggle_browser": "Browser notifications",
-  "notification_toggle_background": "Browser and background notifications",
+  "notification_toggle_background": "Background notifications",
   "display_name_dialog_title": "Change display name",
   "display_name_dialog_description": "Set an alternative name for a topic that is displayed in the subscription list. This helps identify topics with complicated names more easily.",
   "display_name_dialog_placeholder": "Display name",
@@ -169,8 +169,7 @@
   "subscribe_dialog_subscribe_description": "Topics may not be password-protected, so choose a name that's not easy to guess. Once subscribed, you can PUT/POST notifications.",
   "subscribe_dialog_subscribe_topic_placeholder": "Topic name, e.g. phil_alerts",
   "subscribe_dialog_subscribe_use_another_label": "Use another server",
-  "subscribe_dialog_subscribe_enable_browser_notifications_label": "Notify me via browser notifications",
-  "subscribe_dialog_subscribe_enable_background_notifications_label": "Also notify me when ntfy is not open (web push)",
+  "subscribe_dialog_subscribe_enable_background_notifications_label": "Enable background notifications (web push)",
   "subscribe_dialog_subscribe_base_url_label": "Service URL",
   "subscribe_dialog_subscribe_button_generate_topic_name": "Generate name",
   "subscribe_dialog_subscribe_button_cancel": "Cancel",