feat: sprints with burndown and carry-over

Plan sprints with dates and a goal, run one at a time per project, and
put tickets in them from the ticket page. The Sprints tab follows the one
under way with its progress and a burndown in tickets or points against
the ideal line. Closing a sprint sends what was left to the next one or
back to the backlog; the board can be filtered by sprint.

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

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

@@ -44,6 +44,12 @@ export const trackerRoutes: Routes = [
         loadComponent: () =>
           import('./pages/backlog.page').then((m) => m.BacklogPage),
       },
+      {
+        path: 'sprints',
+        title: 'Sprints · TaskStream',
+        loadComponent: () =>
+          import('./pages/sprints.page').then((m) => m.SprintsPage),
+      },
       {
         path: 'epics',
         title: 'Épicas · TaskStream',