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/src/composables/useOrganisationContext.ts

@@ -0,0 +1,28 @@
+import { useCookie } from '@core/composable/useCookie'
+import { computed } from 'vue'
+
+export interface AuthOrganisationSummary {
+  id: string
+  name: string
+  slug: string
+  role: string
+}
+
+export interface AuthUserCookie {
+  id: string
+  name: string
+  email: string
+  roles?: string[]
+  organisations?: AuthOrganisationSummary[]
+}
+
+/**
+ * First organisation from the session cookie (set at login). Super-admins still need an organisation context for nested event routes.
+ */
+export function useCurrentOrganisationId() {
+  const userData = useCookie<AuthUserCookie | null>('userData')
+
+  const organisationId = computed(() => userData.value?.organisations?.[0]?.id ?? null)
+
+  return { organisationId }
+}