feat: notifications in the app and, optionally, by e-mail

Derived from events and kept per person: whoever a ticket is assigned to,
whoever reports or works on it when it moves, fails QA or gets a comment,
and whoever joins a project. Never about what you did yourself, once per
event. They arrive live through a subscription to a bell in the header,
and are copied by e-mail to whoever turns it on when SMTP_URL is set.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/tracker/infrastructure/src/lib/adapters/graphql-notifications.gateway.ts

@@ -0,0 +1,49 @@
+import { inject, Injectable } from '@angular/core';
+import {
+  Notification,
+  NotificationSettings,
+  NotificationsGateway,
+} from '@task-stream/web/tracker/domain';
+import { map, Observable } from 'rxjs';
+import {
+  MarkNotificationsReadDocument,
+  MyNotificationsDocument,
+  NotificationSettingsDocument,
+  UpdateNotificationSettingsDocument,
+} from '../graphql/generated';
+import { GraphqlOperations } from './graphql-operations';
+
+@Injectable()
+export class GraphqlNotificationsGateway extends NotificationsGateway {
+  private readonly gql = inject(GraphqlOperations);
+
+  mine(
+    unreadOnly: boolean,
+    limit: number,
+  ): Observable<{ items: Notification[]; unread: number }> {
+    return this.gql.query(MyNotificationsDocument, { unreadOnly, limit }).pipe(
+      map(({ myNotifications }) => ({
+        unread: myNotifications.unread,
+        items: myNotifications.items as Notification[],
+      })),
+    );
+  }
+
+  markRead(ids?: string[]): Observable<void> {
+    return this.gql
+      .mutate(MarkNotificationsReadDocument, { ids: ids ?? null })
+      .pipe(map(() => undefined));
+  }
+
+  settings(): Observable<NotificationSettings> {
+    return this.gql
+      .query(NotificationSettingsDocument)
+      .pipe(map((d) => ({ ...d.notificationSettings })));
+  }
+
+  updateSettings(email: boolean): Observable<NotificationSettings> {
+    return this.gql
+      .mutate(UpdateNotificationSettingsDocument, { email })
+      .pipe(map((d) => ({ ...d.updateNotificationSettings })));
+  }
+}

libs/web/tracker/infrastructure/src/lib/adapters/graphql-realtime.gateway.ts

@@ -4,6 +4,7 @@ import {
   Activity,
   CommentChanged,
   IssueChanged,
+  Notification,
   ProjectChanged,
   Release,
   TrackerRealtimeGateway,
@@ -14,6 +15,7 @@ import {
   CommentChangedDocument,
   IssueChangedDocument,
   MyProjectsChangedDocument,
+  NotificationAddedDocument,
   ProjectChangedDocument,
   ReleaseChangedDocument,
 } from '../graphql/generated';
@@ -98,6 +100,14 @@ export class GraphqlRealtimeGateway extends TrackerRealtimeGateway {
         .pipe(map((d) => toProjectChanged(d.myProjectsChanged))),
     );
   }
+
+  notifications(): Observable<Notification> {
+    return this.signedIn(() =>
+      this.gql
+        .subscribe(NotificationAddedDocument)
+        .pipe(map((d) => d.notificationAdded as Notification)),
+    );
+  }
 }
 
 const toProjectChanged = (change: {