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/infrastructure/src/lib/adapters/graphql-issues.gateway.ts

@@ -59,6 +59,7 @@ export class GraphqlIssuesGateway extends IssuesGateway {
         labels: filter.labels?.length ? filter.labels : null,
         search: filter.search?.trim() || null,
         unassigned: filter.unassigned ?? null,
+        sprintId: filter.sprintId ?? null,
       })
       .pipe(
         map((d) =>