feat: push notifications on each device (Web Push)

- What reaches the bell also reaches the devices where the person
  turned «Avisos en este dispositivo» on, with TaskStream closed: the
  Notifier sends each new notification encrypted (aes128gcm) and signed
  with VAPID, and forgets subscriptions the push service dropped
  (404/410). A failure never blocks the event stream.
- The API keeps one subscription per device (push_subscriptions) and
  exposes the VAPID public key in the notification settings; GraphQL
  subscribePush/unsubscribePush, REST /me/push-subscriptions. Without
  VAPID_PUBLIC_KEY and VAPID_PRIVATE_KEY push is off.
- The web registers /push-sw.js, a service worker that only shows the
  notification and opens its ticket on a tap (no caching, served
  without cache by nginx), and a manifest that makes it installable,
  which iPhones need for push.
- The bell's toggles show their text next to them.

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

libs/api/tracker/presenters/src/lib/graphql/inputs.ts

@@ -689,3 +689,14 @@ export class ProjectSettingsInput {
   @Type(() => AreaOptionInput)
   areas!: AreaOptionInput[];
 }
+
+@InputType({
+  description: "A browser's Web Push subscription (PushSubscription.toJSON())",
+})
+export class PushSubscriptionInput {
+  @Field()
+  @IsUrl({ protocols: ['https'], require_tld: false })
+  endpoint!: string;
+  @Field() @IsString() @MaxLength(200) p256dh!: string;
+  @Field() @IsString() @MaxLength(100) auth!: string;
+}