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/src/components/form/registry.ts

@@ -8,9 +8,11 @@
 // hold no form value either, but they render on create and update.
 // Phase 12.2 adds the fileupload control: it edits its files through the file
 // routes against the form's session key (D-02, D-03), so it holds no form
-// value either and renders on create and update.
+// value either and renders on create and update. The datepicker control is
+// a plain value field: its string value is part of the save body (D-18).
 import type { Component } from 'vue'
 import CheckboxField from './fields/CheckboxField.vue'
+import DatepickerField from './fields/DatepickerField.vue'
 import DropdownField from './fields/DropdownField.vue'
 import FileuploadField from './fields/FileuploadField.vue'
 import NumberField from './fields/NumberField.vue'
@@ -44,6 +46,7 @@ const renderers = new Map<string, Component>([
   ['widget', WidgetField],
   ['partial', PartialField],
   ['fileupload', FileuploadField],
+  ['datepicker', DatepickerField],
 ])
 
 /** Types whose control shows the label itself (toggle cards, relation manager). */