feat: a sprint calendar

A Calendario tab lays the project's sprints out month by month as bands,
with the releases and the tickets due on each day. Owners and admins plan
a sprint by clicking the day it starts, and the whole plan downloads as an
iCalendar file. Tickets can be searched by due-date range.

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

libs/web/tracker/presenters/src/lib/tracker.routes.ts

@@ -50,6 +50,12 @@ export const trackerRoutes: Routes = [
         loadComponent: () =>
           import('./pages/sprints.page').then((m) => m.SprintsPage),
       },
+      {
+        path: 'calendar',
+        title: 'Calendario · TaskStream',
+        loadComponent: () =>
+          import('./pages/calendar.page').then((m) => m.CalendarPage),
+      },
       {
         path: 'roadmap',
         title: 'Hoja de ruta · TaskStream',