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/commands/command-handlers.ts

@@ -29,6 +29,7 @@ import { AttachFileCommandHandler } from './attach-file.command-handler';
 import { DetachFileCommandHandler } from './detach-file.command-handler';
 import { WatchIssueCommandHandler } from './watch-issue.command-handler';
 import { SetIssueParentCommandHandler } from './set-issue-parent.command-handler';
+import { RankIssueCommandHandler } from './rank-issue.command-handler';
 import { DetachFromParentCommandHandler } from './detach-from-parent.command-handler';
 import {
   AddChecklistItemCommandHandler,
@@ -69,6 +70,7 @@ export const COMMAND_HANDLERS = [
   DetachFileCommandHandler,
   WatchIssueCommandHandler,
   SetIssueParentCommandHandler,
+  RankIssueCommandHandler,
   AddChecklistItemCommandHandler,
   UpdateChecklistItemCommandHandler,
   RemoveChecklistItemCommandHandler,