feat: public projects, project deletion and sagas

Public projects:
- Project.isPublic (create/update, owners and admins). Anyone can read a
  public project without a token: project, board, tickets, comments,
  history, releases, activity, tracking and statistics, over GraphQL and
  REST. Writes stay for members (401 anonymous, 403 outsiders).
- @OptionalAuth() / @ApiOptionalPireonAuth(): anonymous callers allowed,
  invalid tokens still rejected. ReadAccess lets anonymous viewers read
  public projects only; linked tickets are filtered by visibility.
- publicProjects (GraphQL) and GET /api/explore/projects (REST).
- Web: «Explorar» page, project pages open without a session (read-only
  notice, sign-in hints), public badge, visibility switch in settings,
  no realtime subscriptions without a session.

Project deletion:
- Owner only, confirming the key (deleteProject / DELETE
  /api/projects/{project}?confirm=KEY). The key is freed; the read model
  drops the project and members are notified (web goes home).

Sagas (run by the EventsBridge after projections, durable and ordered):
- ProjectDeletionSaga: project deleted → delete its tickets and releases;
  ticket deleted → purge its comments and drop links from other tickets.
- ReleaseArchivedSaga: unfinished tickets leave an archived release.
- UserDeactivatedSaga: the Pireon webhook records UserDeactivatedEvent in
  the event store (EventRecorder); the tracker unassigns that user's open
  tickets as the system actor.
- Internal idempotent commands; domain refusals are logged and skipped,
  concurrency conflicts retried. Affected streams come from the event store
  (TrackerStreamsRepository).

Tests: domain lifecycle specs, saga specs run like the bridge, facade
tests, e2e for public access, cascade deletion, archived releases and
deactivation webhook. Docs, READMEs, schema.gql/openapi.json and Word/PDF
updated.

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

libs/api/tracker/presenters/README.md

@@ -12,6 +12,8 @@ API GraphQL y REST (OpenAPI) del tracker.
 - `http/`: controladores REST `ProjectsController`, `IssuesController`, `CommentsController`, `ReleasesController`
   (mismos services), DTOs con `@nestjs/swagger` y `Refs` (proyectos y tickets por id o clave; añade a cada ticket sus
   transiciones permitidas según el workflow de su proyecto).
+- `ExploreController` (`GET /api/explore/projects`, sin token). Las lecturas usan `@OptionalAuth()` y `viewerOf(me)`
+  (null = anónimo) para servir proyectos públicos sin sesión.
 - `common/settings.ts`: configuración del proyecto con las transiciones como lista (lo que viaja por GraphQL y REST).
 
 Operaciones disponibles: [GraphQL](../../../../docs/03-api.md#32-graphql) y