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/presenters/src/lib/pages/project-shell.page.ts

@@ -85,6 +85,7 @@ import { projectTone, PUBLIC_TONE, ROLE } from '../ui/copy';
       }
       <nav class="ts-tabs" aria-label="Secciones del proyecto">
         <a routerLink="board" routerLinkActive="is-active">Tablero</a>
+        <a routerLink="backlog" routerLinkActive="is-active">Backlog</a>
         <a routerLink="epics" routerLinkActive="is-active">Épicas</a>
         <a routerLink="releases" routerLinkActive="is-active">Releases</a>
         <a routerLink="dashboard" routerLinkActive="is-active">Seguimiento</a>