feat: archive a project instead of deleting it

The owner archives a finished project (archiveProject, POST
/projects/{project}/archive) and brings it back (unarchive). While
archived it stays readable, managers still read its rules and webhooks,
but no command changes it: contributing and managing checks refuse with
422, votes and public proposals too, and automations do not run. The web
shows a read-only notice on every page of it (with «Desarchivar» for the
owner), hides what edits, marks it on the home page and lists it last.

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

libs/api/tracker/domain/src/lib/project/project.ts

@@ -4,6 +4,10 @@ import {
   VersionedAggregateRoot,
   assertThat,
 } from '@task-stream/api/shared/domain';
+import {
+  ProjectArchivedEvent,
+  ProjectUnarchivedEvent,
+} from '../events/project-archived.event';
 import { ProjectCreatedEvent } from '../events/project-created.event';
 import { ProjectDeletedEvent } from '../events/project-deleted.event';
 import { ProjectMemberAddedEvent } from '../events/project-member-added.event';
@@ -62,6 +66,8 @@ export class Project extends VersionedAggregateRoot implements ProjectProps {
   public updatedAt!: string;
   /** Set once deleted: the project can no longer be loaded for commands. */
   public deleted = false;
+  /** Archived since then: read-only until its owner brings it back. */
+  public archivedAt: string | null = null;
 
   constructor(id: string) {
     super();
@@ -96,10 +102,20 @@ export class Project extends VersionedAggregateRoot implements ProjectProps {
     if (this.roleOf(userId) === ProjectRole.VIEWER) {
       throw new ForbiddenError(`Viewers cannot modify project ${this.key}`);
     }
+    this.assertNotArchived();
   }
 
-  /** Can manage members, releases and project settings. */
+  /** Can change members, releases, settings and rules (owners and admins). */
   assertCanManage(userId: string): void {
+    this.assertManages(userId);
+    this.assertNotArchived();
+  }
+
+  /**
+   * Is an owner or an admin: enough to read what only they see (rules,
+   * webhooks…), archived or not. To change anything, assertCanManage.
+   */
+  assertManages(userId: string): void {
     const role = this.roleOf(userId);
     if (role !== ProjectRole.OWNER && role !== ProjectRole.ADMIN) {
       throw new ForbiddenError(
@@ -108,6 +124,36 @@ export class Project extends VersionedAggregateRoot implements ProjectProps {
     }
   }
 
+  /** An archived project only changes back to active (by its owner). */
+  assertNotArchived(): void {
+    if (this.archivedAt)
+      throw new BusinessRuleError(
+        `${this.key} está archivado: es de solo lectura hasta que su propietario lo desarchive`,
+      );
+  }
+
+  /**
+   * Only the owner archives a project: everything stays readable, nothing
+   * changes until they unarchive it. Idempotent.
+   */
+  archive(actorId: string): void {
+    if (actorId !== this.ownerId)
+      throw new ForbiddenError(
+        `Only the owner can archive project ${this.key}`,
+      );
+    if (this.archivedAt) return;
+    this.apply(new ProjectArchivedEvent(actorId, this.id));
+  }
+
+  unarchive(actorId: string): void {
+    if (actorId !== this.ownerId)
+      throw new ForbiddenError(
+        `Only the owner can unarchive project ${this.key}`,
+      );
+    if (!this.archivedAt) return;
+    this.apply(new ProjectUnarchivedEvent(actorId, this.id));
+  }
+
   updateDetails(
     actorId: string,
     changes: {
@@ -249,6 +295,14 @@ export class Project extends VersionedAggregateRoot implements ProjectProps {
     this.deleted = true;
   }
 
+  onProjectArchivedEvent(event: ProjectArchivedEvent): void {
+    this.archivedAt = event.occurredAt;
+  }
+
+  onProjectUnarchivedEvent(): void {
+    this.archivedAt = null;
+  }
+
   onProjectSettingsChangedEvent(event: ProjectSettingsChangedEvent): void {
     this.settings = structuredClone(event.settings);
     this.updatedAt = event.occurredAt;