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>

apps/api/schema.gql

@@ -118,6 +118,9 @@ input CreateIssueInput {
 input CreateProjectInput {
   description: String
 
+  """Readable by anyone, also without signing in"""
+  isPublic: Boolean
+
   """2-10 chars, e.g. "TS" → tickets TS-1, TS-2..."""
   key: String!
   name: String!
@@ -312,6 +315,11 @@ type Mutation {
 
   """Author or project admin"""
   deleteComment(commentId: ID!): CommandResult!
+
+  """
+  Delete the project (owner only), with its tickets, comments and releases. `confirmKey` must be the project key.
+  """
+  deleteProject(confirmKey: String!, projectId: ID!): CommandResult!
   editComment(body: String!, commentId: ID!): CommandResult!
 
   """Relate tickets, e.g. FE DEPENDS_ON BE, QA TESTS FE"""
@@ -347,6 +355,9 @@ type Project {
   createdAt: String!
   description: String
   id: ID!
+
+  """Anyone can read it, also without signing in"""
+  isPublic: Boolean!
   key: String!
   members: [ProjectMember!]!
   name: String!
@@ -467,10 +478,15 @@ type Query {
 
   """Projects where I am a member"""
   myProjects: [Project!]!
+
+  """A project of mine, or any public one (no sign-in needed)"""
   project(
     """Project id or key (e.g. "TS")"""
     idOrKey: String!
   ): Project!
+
+  """Projects anyone can read, also without signing in"""
+  publicProjects: [Project!]!
   release(id: ID!): Release!
 
   """Planned releases of all my projects, soonest target date first"""
@@ -593,6 +609,7 @@ input UpdateIssueInput {
 
 input UpdateProjectInput {
   description: String
+  isPublic: Boolean
   name: String
   projectId: ID!
 }