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/application/src/lib/events/issue.events.ts

@@ -26,6 +26,10 @@ export const issuePageEvents = eventGroup({
       targetKey: string;
     }>(),
     unlinkRequested: type<LinkIssuesInput>(),
+    sprintChangeRequested: type<{
+      issueId: string;
+      sprintId: string | null;
+    }>(),
     releaseChangeRequested: type<{
       issueId: string;
       releaseId: string | null;