feat: guest role for clients and outsiders

A project member can be a GUEST. In a private project a guest only sees
the tickets they take part in (opened, assigned or followed): every other
ticket answers 404, also in my work, realtime changes, blockers and
linked tickets, and project-wide views (activity, statistics, dashboard,
releases, sprints, epics, trash) answer 403. Guests open tickets without
assigning or planning them, and comment, attach, follow and vote on their
own; they change nothing else. In a public project they see what anyone
does. The web gives them only Tablero, Lista and Miembros and loads none
of the project-wide data.

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

libs/api/tracker/application/src/lib/queries/get-issue.query-handler.ts

@@ -18,7 +18,7 @@ export class GetIssueQueryHandler
       ? await this.findIssues.findById(query.idOrKey)
       : await this.findIssues.findByKey(query.idOrKey.toUpperCase());
     const found = this.access.assertFound(issue, 'Issue', query.idOrKey);
-    await this.access.assertCanView(found.projectId, query.viewerId, {
+    await this.access.assertCanViewIssue(found, query.viewerId, {
       entity: 'Issue',
       ref: query.idOrKey,
     });