test(10-05): bring every SPA module, composable and component under Vitest

- 41 unit and component suites under admin/tests/{app,state,shell,list,form,relation,views,ui}
  covering states and a11y roles; every src module is imported by a test
- typed fixture helper assigns each JSON fixture to its generated OpenAPI type
- fix: iconFor ignores inherited object members such as "constructor"
- fix: field controls import ./control instead of the registry (import cycle
  left a renderer unregistered depending on module load order)
- fix: dropdown shows the placeholder for an unknown stored value next to an emptyOption
- fix: list announces a failed schema load even when the rows arrive after it
- tailwind no longer scans admin/tests; boardwalk/dist rebuilt

admin/src/components/relation/RelationManager.vue

@@ -11,7 +11,7 @@ import Pagination from '../list/Pagination.vue'
 import Button from '../ui/Button.vue'
 import ConfirmDialog from '../ui/ConfirmDialog.vue'
 import { useConfirm } from '../ui/confirm'
-import type { FieldControlProps } from '../form/registry'
+import type { FieldControlProps } from '../form/control'
 import RelationPickerModal from './RelationPickerModal.vue'
 
 // Relation manager field (D-05, design screen 5). Renders only for an