feat: presence on tickets

A ticket's page beats every 10 s (touchPresence / PUT
/issues/{issue}/presence, with whether I am editing) and gets back who
else is there, editing ones first. Entries live in Redis, one hash per
ticket, and fade after 30 s without a beat; leaving the page takes me out
at once. Only for people who can read the ticket; never in the event
store. The ticket shows «Bob está editando · Ana también lo está viendo»
above its title; editing means a ticket or comment form is open or a
comment is being written.

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

libs/api/tracker/application/src/index.ts

@@ -32,3 +32,5 @@ export * from './lib/saved-filters/saved-filters';
 export * from './lib/saved-filters/my-views';
 export * from './lib/ports/my-views.repository';
 export * from './lib/tracker-application.module';
+export * from './lib/ports/presence.store';
+export * from './lib/presence.service';