feat(16.2-01): translatable plugin fields, element uploads and save notices in the admin

- MLPluginField wraps PluginField in the MLField locale switcher; the
  element gets the active content locale and that locale's string
- isMLField treats a translatable plugin field as a locale map in the form
  state, FormView adopt and the relation child modal
- summer-upload posts the file with the admin session to the field upload
  route and answers summer-upload-result {id, url} or {id, error}
- noticeLines shows meta.notices under each field as a warning status line
  (text only) and in the saved toast; the stored value is reloaded
- docs/backend/field-types.md documents the full element contract;
  modules/boardwalk/dist rebuilt

admin/tests/list/CellValue.test.ts

@@ -17,6 +17,14 @@ beforeEach(() => {
   resetState()
 })
 
+describe('plugin field type columns (16.2)', () => {
+  it('renders the ListValue text of a plugin type as plain text', () => {
+    const wrapper = cell({ ...text, type: 'notes' }, '<b>3 blocks</b>')
+    expect(wrapper.text()).toBe('<b>3 blocks</b>')
+    expect(wrapper.find('b').exists()).toBe(false)
+  })
+})
+
 describe('cell value (D-12)', () => {
   it.each([
     ['a string', 'Blue', 'Blue'],