feat(12.2-04): add the datepicker field and stored date and time list cells

- pin @internationalized/date 3.12.4 as a direct admin dependency (approved)
- dateFormat.ts parses and emits date, datetime (local display, UTC emit,
  ignoreTimezone wall clock) and time values without the global Date
- DatepickerField on Reka DatePicker and TimeField with locale segments,
  calendar popover, clear button, min/max and yearRange bounds
- list cells of type date and time render the stored string
- datepicker lang keys in en and pl; rebuilt boardwalk dist

admin/tests/fixtures/deferred.form-schema.json

@@ -8,6 +8,20 @@
         "type": "text",
         "required": true
       },
+      {
+        "name": "starts_at",
+        "label": "Starts at",
+        "type": "datepicker",
+        "mode": "datetime"
+      },
+      {
+        "name": "released_on",
+        "label": "Released on",
+        "type": "datepicker",
+        "mode": "date",
+        "minDate": "2026-01-01",
+        "displayFormat": "D MMMM YYYY"
+      },
       {
         "name": "photos",
         "label": "Photos",

admin/tests/smoke/deferred.smoke.test.ts

@@ -2,9 +2,12 @@
 // record's form makes one session key, uploads go to record id 0 with that
 // key in a header, the form turns dirty, and the create save sends the same
 // key so the server can attach the files. The upload XMLHttpRequest is
-// replaced by a fake the test answers by hand.
+// replaced by a fake the test answers by hand. The datepicker part runs in a
+// fixed non-UTC zone: a stored UTC instant shows as local time and goes back
+// unchanged, a date goes out as YYYY-MM-DD.
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
-import { flushPromises, type VueWrapper } from '@vue/test-utils'
+import { flushPromises, type DOMWrapper, type VueWrapper } from '@vue/test-utils'
+import { resetLocalTimeZone, setLocalTimeZone } from '@internationalized/date'
 import { setBundle } from '../../src/app/i18n'
 import { SESSION_HEADER } from '../../src/app/sessionKey'
 import { clearUser } from '../../src/state/useAuth'
@@ -210,3 +213,97 @@ describe('fileupload on a new record (tracer)', () => {
     expect((FakeXHR.sent[1]!.body!.get('file_data') as File).name).toBe('b.png')
   })
 })
+
+const saved = {
+  data: { id: 7, name: 'Box', starts_at: '2026-10-02T10:30:00Z', released_on: null },
+  meta: { labels: {} },
+}
+
+function editRoutes(): Record<string, Route> {
+  return routes({
+    [`GET ${BASE}/7`]: { body: saved },
+    [`GET ${BASE}/7/files/photos`]: { body: { data: [], meta: {} } },
+    [`PUT ${BASE}/7`]: { body: saved },
+  })
+}
+
+function segment(field: DOMWrapper<Element>, part: string): DOMWrapper<Element> {
+  return field.find(`[data-reka-date-field-segment="${part}"]`)
+}
+
+async function typeInto(field: DOMWrapper<Element>, part: string, digits: string): Promise<void> {
+  const target = segment(field, part)
+  for (const key of digits) {
+    await target.trigger('keydown', { key })
+  }
+}
+
+describe('datepicker values in a fixed time zone', () => {
+  beforeEach(() => setLocalTimeZone('Europe/Warsaw'))
+  afterEach(() => resetLocalTimeZone())
+
+  it('shows a stored datetime in local time, saves it unchanged and sends a typed date as YYYY-MM-DD', async () => {
+    const { wrapper, calls } = await mountApp('/acme/demo/gadgets/7', editRoutes())
+
+    const starts = wrapper.find('[data-field="starts_at"]')
+    expect(segment(starts, 'hour').text()).toBe('12')
+    expect(segment(starts, 'minute').text()).toBe('30')
+    expect(segment(starts, 'timeZoneName').exists()).toBe(true)
+    // Not required and set: the clear button is offered next to the trigger.
+    expect(starts.find('[data-action="clear"]').attributes('aria-label')).toBe('backend::lang.datepicker.clear')
+    expect(starts.find('[data-action="open-calendar"]').attributes('aria-label')).toBe(
+      'backend::lang.datepicker.open_calendar',
+    )
+    // The label points at the field's id; no native date input is rendered by the field itself.
+    expect(wrapper.find('label[for="field-starts_at"]').exists()).toBe(true)
+
+    const released = wrapper.find('[data-field="released_on"]')
+    expect(segment(released, 'day').attributes('data-placeholder')).toBeDefined()
+    // Polish segment order: day, month, year.
+    const parts = released
+      .findAll('[data-reka-date-field-segment]')
+      .map((el) => el.attributes('data-reka-date-field-segment'))
+      .filter((part) => part !== 'literal' && part !== 'trigger')
+    expect(parts).toEqual(['day', 'month', 'year'])
+
+    await typeInto(released, 'day', '02')
+    await typeInto(released, 'month', '10')
+    await typeInto(released, 'year', '2026')
+    await flushPromises()
+
+    await wrapper.find('[data-action="save"]').trigger('click')
+    await flushPromises()
+    const [put] = requestsTo(calls, 'PUT', `${BASE}/7`)
+    expect(put).toBeDefined()
+    const body = await put!.clone().json()
+    expect(body.starts_at).toBe('2026-10-02T10:30:00Z')
+    expect(body.released_on).toBe('2026-10-02')
+  })
+
+  it('converts an edited local time back to UTC', async () => {
+    const { wrapper, calls } = await mountApp('/acme/demo/gadgets/7', editRoutes())
+
+    const starts = wrapper.find('[data-field="starts_at"]')
+    await segment(starts, 'minute').trigger('keydown', { key: 'ArrowUp' })
+    await flushPromises()
+    expect(segment(starts, 'minute').text()).toBe('31')
+
+    await wrapper.find('[data-action="save"]').trigger('click')
+    await flushPromises()
+    const [put] = requestsTo(calls, 'PUT', `${BASE}/7`)
+    expect((await put!.clone().json()).starts_at).toBe('2026-10-02T10:31:00Z')
+  })
+
+  it('clears an optional value to null', async () => {
+    const { wrapper, calls } = await mountApp('/acme/demo/gadgets/7', editRoutes())
+
+    await wrapper.find('[data-field="starts_at"] [data-action="clear"]').trigger('click')
+    await flushPromises()
+    expect(wrapper.find('[data-field="starts_at"] [data-action="clear"]').exists()).toBe(false)
+
+    await wrapper.find('[data-action="save"]').trigger('click')
+    await flushPromises()
+    const [put] = requestsTo(calls, 'PUT', `${BASE}/7`)
+    expect((await put!.clone().json()).starts_at).toBeNull()
+  })
+})