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/web/tracker/infrastructure/src/lib/adapters/graphql-issues.gateway.ts

@@ -18,6 +18,7 @@ import { map, Observable } from 'rxjs';
 import {
   AddChecklistItemDocument,
   AssignIssueDocument,
+  BacklogDocument,
   BoardDocument,
   ChangeIssueStatusDocument,
   CreateIssueDocument,
@@ -26,6 +27,7 @@ import {
   IssueDocument,
   LinkIssuesDocument,
   MyIssuesDocument,
+  RankIssueDocument,
   RemoveChecklistItemDocument,
   SearchIssuesDocument,
   SetIssueParentDocument,
@@ -166,6 +168,31 @@ export class GraphqlIssuesGateway extends IssuesGateway {
     );
   }
 
+  backlog(projectId: string): Observable<IssuePage> {
+    return this.gql
+      .query(BacklogDocument, {
+        filter: { projectId, categories: ['TODO'], sort: 'RANK' },
+      })
+      .pipe(
+        map((d) => ({
+          items: d.issues.items.map(toIssueSummary),
+          total: d.issues.total,
+        })),
+      );
+  }
+
+  rank(
+    issueId: string,
+    aboveIssueId: string | null,
+    belowIssueId: string | null,
+  ): Observable<CommandResult> {
+    return this.gql
+      .mutate(RankIssueDocument, {
+        input: { issueId, aboveIssueId, belowIssueId },
+      })
+      .pipe(map((d) => toCommandResult(d.rankIssue)));
+  }
+
   addChecklistItem(issueId: string, text: string): Observable<CommandResult> {
     return this.gql
       .mutate(AddChecklistItemDocument, { input: { issueId, text } })