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/event-handlers/event-handlers.ts

@@ -30,6 +30,7 @@ import { AttachmentCleanupEventHandler } from './attachment-cleanup.event-handle
 import { IssueWatchersEventHandler } from './issue-watchers.event-handler';
 import { IssueParentChangedEventHandler } from './issue-parent-changed.event-handler';
 import { IssueChecklistEventHandler } from './issue-checklist.event-handler';
+import { IssueRankedEventHandler } from './issue-ranked.event-handler';
 
 /** Read-model projections (MongoDB) + realtime, fed by the EventsBridge. */
 export const EVENT_HANDLERS = [
@@ -64,6 +65,7 @@ export const EVENT_HANDLERS = [
   IssueWatchersEventHandler,
   IssueParentChangedEventHandler,
   IssueChecklistEventHandler,
+  IssueRankedEventHandler,
 ];
 
 export { ReadModelNotifier };