feat: archive a project instead of deleting it

The owner archives a finished project (archiveProject, POST
/projects/{project}/archive) and brings it back (unarchive). While
archived it stays readable, managers still read its rules and webhooks,
but no command changes it: contributing and managing checks refuse with
422, votes and public proposals too, and automations do not run. The web
shows a read-only notice on every page of it (with «Desarchivar» for the
owner), hides what edits, marks it on the home page and lists it last.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/tracker/presenters/src/lib/ui/project-card.ts

@@ -25,6 +25,9 @@ import { projectTone, PUBLIC_TONE, timeAgo } from './copy';
         @if (project().isPublic) {
           <span class="ts-pill" [style.--tone]="publicTone">Público</span>
         }
+        @if (project().archivedAt) {
+          <span class="ts-pill">Archivado</span>
+        }
         <span class="ts-project__updated ts-mono">{{
           ago(project().updatedAt)
         }}</span>