refactor: align codebase with EventCrew domain and trim legacy band stack

- Update API: events, users, policies, routes, resources, migrations
- Remove deprecated models/resources (customers, setlists, invitations, etc.)
- Refresh admin app and docs; remove apps/band

Made-with: Cursor

apps/admin/index.html

@@ -6,7 +6,7 @@
   <link rel="icon" href="/favicon.ico" />
   <meta name="robots" content="noindex, nofollow" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>Band Management Admin</title>
+  <title>Event Crew Admin</title>
   <link rel="stylesheet" type="text/css" href="/loader.css" />
 </head>