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/api/tracker/domain/src/lib/read-models/sprint.read-model.ts

@@ -0,0 +1,40 @@
+import { SprintStatus } from '../sprint/sprint-status';
+
+export class SprintReadModel {
+  id!: string;
+  projectId!: string;
+  name!: string;
+  goal!: string | null;
+  /** `YYYY-MM-DD`, both included. */
+  startDate!: string;
+  endDate!: string;
+  status!: SprintStatus;
+  startedAt!: string | null;
+  closedAt!: string | null;
+  createdAt!: string;
+  version!: number;
+}
+
+/** How far a sprint's tickets have got. */
+export class SprintProgressReadModel {
+  total!: number;
+  /** Done or cancelled. */
+  finished!: number;
+  percent!: number;
+  storyPoints!: number;
+  finishedStoryPoints!: number;
+}
+
+/**
+ * Per day of the sprint: tickets in it (cancelled ones aside), how many are
+ * still open and their points. Days still to come are null; `ideal` falls in
+ * a straight line from what was open on the first day to zero on the last.
+ */
+export class SprintBurndownReadModel {
+  sprintId!: string;
+  dates!: string[];
+  scope!: (number | null)[];
+  remaining!: (number | null)[];
+  remainingPoints!: (number | null)[];
+  ideal!: number[];
+}