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/presenters/src/lib/graphql/issue.resolver.ts

@@ -28,6 +28,7 @@ import {
   CreateIssueInput,
   IssueFilterInput,
   LinkIssuesInput,
+  RankIssueInput,
   UpdateChecklistItemInput,
   UpdateIssueInput,
 } from './inputs';
@@ -266,6 +267,19 @@ export class IssueResolver {
     return this.issuesService.setParent(me.id, issueId, parentId ?? null);
   }
 
+  @Mutation(() => CommandResultGql, {
+    description:
+      'Move a ticket in the backlog, between two others of the same project',
+  })
+  rankIssue(@CurrentUser() me: User, @Args('input') input: RankIssueInput) {
+    return this.issuesService.rank(
+      me.id,
+      input.issueId,
+      input.aboveIssueId ?? null,
+      input.belowIssueId ?? null,
+    );
+  }
+
   @Mutation(() => CommandResultGql, {
     description: "Add a step to a ticket's checklist",
   })