feat: a calendar to subscribe to, and the backlog's corners

- Each person can subscribe their dates in Google Calendar, Outlook or
  Apple Calendar: GET /api/calendar/{token}.ics (no session) brings
  their unfinished tickets with a due date (assigned or followed), the
  planned and running sprints and the planned releases of their
  projects, as all-day events linking to the web. The token is made,
  renewed or dropped under /me/calendar (and in GraphQL); in the web,
  from «Calendario» in «Mi trabajo».
- The backlog panel keeps the selected rows' background inside its
  rounded corners.

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

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

@@ -27,3 +27,4 @@ export * from './git-integrations.repository';
 export * from './outgoing-webhooks.repository';
 export * from './automations.repository';
 export * from './rate-limit.store';
+export * from './calendar-feeds.repository';