feat: an ordered backlog

A Backlog tab lists the tickets still to start in the order the team will
take them; drag them, or use the arrows, to reorder. Moving a ticket only
rewrites that ticket's rank, read from the event store, and board columns
follow the same order.

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

libs/api/tracker/application/src/lib/queries/get-board.query-handler.ts

@@ -3,7 +3,10 @@ import {
   DEFAULT_PROJECT_SETTINGS,
   StatusCategory,
 } from '@task-stream/api/tracker/domain';
-import { FindIssuesRepository } from '../ports/find-issues.repository';
+import {
+  FindIssuesRepository,
+  IssueSort,
+} from '../ports/find-issues.repository';
 import { FindProjectsRepository } from '../ports/find-projects.repository';
 import { BoardColumn, GetBoardQuery } from './get-board.query';
 import { ReadAccess } from './read-access';
@@ -33,6 +36,8 @@ export class GetBoardQueryHandler
         const page = await this.findIssues.search({
           ...query.filter,
           statuses: [status.id],
+          // Each column follows the backlog order.
+          sort: IssueSort.RANK,
           limit: Math.min(query.perColumn, 200),
           offset: 0,
         });