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/api/tracker/presenters/src/lib/tracker-presenters.module.ts

@@ -3,6 +3,7 @@ import { ConfigService } from '@nestjs/config';
 import { MulterModule } from '@nestjs/platform-express';
 import './graphql/enums';
 import { CommentResolver } from './graphql/comment.resolver';
+import { NotificationResolver } from './graphql/notification.resolver';
 import { IssueResolver } from './graphql/issue.resolver';
 import { ProjectResolver } from './graphql/project.resolver';
 import { ReleaseResolver } from './graphql/release.resolver';
@@ -14,6 +15,7 @@ import { ExploreController } from './http/explore.controller';
 import { ProjectsController } from './http/projects.controller';
 import { Refs } from './http/refs';
 import { ReleasesController } from './http/releases.controller';
+import { NotificationsController } from './http/notifications.controller';
 
 /**
  * Driving adapters of the tracker context: GraphQL (queries, mutations,
@@ -42,6 +44,7 @@ import { ReleasesController } from './http/releases.controller';
     CommentsController,
     ReleasesController,
     ExploreController,
+    NotificationsController,
   ],
   providers: [
     Refs,
@@ -50,6 +53,7 @@ import { ReleasesController } from './http/releases.controller';
     CommentResolver,
     ReleaseResolver,
     SubscriptionResolver,
+    NotificationResolver,
   ],
 })
 export class TrackerPresentersModule {