Correctly handle standalone (PWA) mode changes

- Also handle notification permission changes
- Remove web push schedule worker since this complicates
  things and doesn’t do _that_ much. We have the reminder
  notification if the user truly doesn’t reload ntfy in
  more than a week.

web/src/app/Prefs.js

@@ -1,5 +1,4 @@
 import db from "./db";
-import { isLaunchedPWA } from "./utils";
 
 class Prefs {
   constructor(dbImpl) {
@@ -35,7 +34,7 @@ class Prefs {
 
   async webPushEnabled() {
     const webPushEnabled = await this.db.prefs.get("webPushEnabled");
-    return webPushEnabled?.value ?? isLaunchedPWA();
+    return webPushEnabled?.value;
   }
 
   async setWebPushEnabled(enabled) {