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/form/fields/RelationField.vue

@@ -4,7 +4,7 @@ import { ChevronDown, X } from '@lucide/vue'
 import { api } from '../../../api/client'
 import type { RelationOption } from '../../../api/types'
 import { t } from '../../../app/i18n'
-import type { FieldControlProps } from '../registry'
+import type { FieldControlProps } from '../control'
 
 // Relation field (D-17, D-18, D-26), three modes from the schema:
 //   readOnly  the label from meta.labels only, no control