feat: teams within a project

Projects keep teams of members in their settings (settings.teams; people
outside the project are dropped, teams are archived, not removed; absent
when saving means unchanged). Tickets go to a team (`team`, also filtered
in the list and in MCP search_issues), and a comment mentioning
@[Frontend](team-FRONT) tells each of its members. Settings has the teams
with their members, the ticket a «Equipo» select, the list a team filter,
and «@» offers the teams after the people.

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

libs/api/tracker/domain/src/lib/project/project-settings.spec.ts

@@ -403,4 +403,55 @@ describe('Project settings', () => {
     });
     expect(project.workflow.checklistBeforeDone).toBe(false);
   });
+
+  it('keeps teams of members, assigns tickets to them and expands their mentions', () => {
+    const project = newProject();
+    project.updateSettings('owner', {
+      ...defaultProjectSettings(),
+      teams: [
+        {
+          id: 'front',
+          name: ' Frontend ',
+          memberIds: ['dev', 'dev', 'stranger'],
+          archived: false,
+        },
+      ],
+    });
+    // Normalised, and only people of the project.
+    expect(project.workflow.teams).toEqual([
+      { id: 'FRONT', name: 'Frontend', memberIds: ['dev'], archived: false },
+    ]);
+    // Absent: unchanged; removing one: refused (archive it instead).
+    project.updateSettings('owner', defaultProjectSettings());
+    expect(project.workflow.teams).toHaveLength(1);
+    expect(() =>
+      project.updateSettings('owner', {
+        ...defaultProjectSettings(),
+        teams: [],
+      }),
+    ).toThrow(/archívalo/);
+
+    expect(
+      project.workflow.mentionedPeople(['owner', 'team-FRONT', 'team-NOPE']),
+    ).toEqual(['owner', 'dev']);
+
+    const issue = new IssueFactory().create(
+      {
+        projectId: project.id,
+        projectKey: 'WEB',
+        number: 1,
+        title: 'Botón',
+        type: 'TASK',
+        reporterId: 'dev',
+        team: 'FRONT',
+      },
+      project.workflow,
+    );
+    expect(issue.team).toBe('FRONT');
+    expect(() =>
+      issue.updateDetails('dev', { team: 'NOPE' }, project.workflow),
+    ).toThrow(ValidationError);
+    issue.updateDetails('dev', { team: null }, project.workflow);
+    expect(issue.team).toBeNull();
+  });
 });