Add PWA, service worker and Web Push

- Use new notification request/opt-in flow for push
- Implement unsubscribing
- Implement muting
- Implement emojis in title
- Add iOS specific PWA warning
- Don’t use websockets when web push is enabled
- Fix duplicate notifications
- Implement default web push setting
- Implement changing subscription type
- Implement web push subscription refresh
- Implement web push notification click

web/src/app/SessionReplica.js

@@ -0,0 +1,44 @@
+import Dexie from "dexie";
+
+// Store to IndexedDB as well so that the
+// service worker can access it
+// TODO: Probably make everything depend on this and not use localStorage,
+// but that's a larger refactoring effort for another PR
+
+class SessionReplica {
+  constructor() {
+    const db = new Dexie("session-replica");
+
+    db.version(1).stores({
+      keyValueStore: "&key",
+    });
+
+    this.db = db;
+  }
+
+  async store(username, token) {
+    try {
+      await this.db.keyValueStore.bulkPut([
+        { key: "user", value: username },
+        { key: "token", value: token },
+      ]);
+    } catch (e) {
+      console.error("[Session] Error replicating session to IndexedDB", e);
+    }
+  }
+
+  async reset() {
+    try {
+      await this.db.delete();
+    } catch (e) {
+      console.error("[Session] Error resetting session on IndexedDB", e);
+    }
+  }
+
+  async username() {
+    return (await this.db.keyValueStore.get({ key: "user" }))?.value;
+  }
+}
+
+const sessionReplica = new SessionReplica();
+export default sessionReplica;