feat(forms): add FormField wrapper + useFormError composable per RFC Appendix A

Two new artifacts that together provide the F4 form-migration target:

apps/app/src/components/forms/FormField.vue — project-owned wrapper
around @primevue/forms' built-in FormField. The default slot accepts
the actual input (e.g. <InputText name="email" />); the wrapper renders
label (with optional required asterisk), error Message, and hint chrome
around it. Reads field state from the parent <Form> via the built-in
FormField's scoped slot, so call-sites do not need to thread $form
manually.

apps/app/src/composables/useFormError.ts — the API 422 bridge. Parent
component calls useFormError() once; the composable provides an
apiErrors ref through Vue inject. Each FormField in the component
reads its own field name from that map. applyApiErrors() reads the
Crewli backend's { errors: { field: string[] } } shape and surfaces
the first message per field; clearApiErrors() resets between submits.

Error precedence per RFC Appendix A: explicit apiError prop > inject
apiErrors map > Zod resolver error from $field.

Signature note: RFC's useFormError(formRef) is implemented as
useFormError() — the formRef parameter is unused in the provide/inject
implementation, and Crewli convention avoids unused parameters. RFC
will be aligned in B9 if it remains a meaningful spec gap during F4.

Verification:
- pnpm typecheck — clean.
- pnpm test — 402 tests pass unchanged.
- B8 will exercise the components end-to-end on the login page; F4d
  validates against the public-registration multi-step form.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/app/src/composables/useFormError.ts

@@ -0,0 +1,44 @@
+// useFormError — merges Laravel 422 validation responses into the
+// surrounding Form's per-field error display.
+//
+// Pattern: a parent component calls useFormError() once. The composable
+// provides an apiErrors map via Vue inject. Each FormField inside the
+// component reads its own field name from that map and falls through to
+// its $field.error (the Zod resolver result) when no API error is set.
+// apiError precedence > Zod error per RFC Appendix A.
+//
+// Crewli backend 422 shape: { message, errors: { field: string[] } }.
+// We surface the first message per field.
+
+import { type Ref, provide, ref } from 'vue'
+
+export const FORM_API_ERRORS_KEY = Symbol('crewli-form-api-errors')
+
+export type FormApiErrorsMap = Record<string, string>
+
+export interface UseFormErrorReturn {
+  applyApiErrors: (errors: Record<string, string[]>) => void
+  clearApiErrors: () => void
+  apiErrors: Ref<FormApiErrorsMap>
+}
+
+export function useFormError(): UseFormErrorReturn {
+  const apiErrors = ref<FormApiErrorsMap>({})
+
+  provide(FORM_API_ERRORS_KEY, apiErrors)
+
+  function applyApiErrors(errors: Record<string, string[]>): void {
+    const next: FormApiErrorsMap = {}
+    for (const [field, messages] of Object.entries(errors)) {
+      if (Array.isArray(messages) && messages.length > 0)
+        next[field] = messages[0]
+    }
+    apiErrors.value = next
+  }
+
+  function clearApiErrors(): void {
+    apiErrors.value = {}
+  }
+
+  return { applyApiErrors, clearApiErrors, apiErrors }
+}