feat(12.2-04): add the fileupload field with deferred uploads on the form session key

- sessionKey.ts: one 32-byte base64url key per form mount, sent only in headers
- api/files.ts: FileRoutes over the record and child file routes, XHR upload with progress, 401 refresh and retry
- FileuploadField and FileCaptionModal per UI-SPEC section 3: dropzone, image grid, rows, per-item states, client pre-checks, reorder, protected previews
- FormView provides FORM_SESSION, counts pending changes as dirty and sends X-Session-Key on create and update
- fileupload lang keys in en and pl, admin-spa docs note, deferred smoke test, rebuilt dist

admin/src/components/form/registry.ts

@@ -6,9 +6,13 @@
 // Phase 10.1 adds the plugin extension types: a widget mounts a plugin custom
 // element (D-04, D-09) and a partial renders a server template (D-17). They
 // 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.
 import type { Component } from 'vue'
 import CheckboxField from './fields/CheckboxField.vue'
 import DropdownField from './fields/DropdownField.vue'
+import FileuploadField from './fields/FileuploadField.vue'
 import NumberField from './fields/NumberField.vue'
 import PartialField from './fields/PartialField.vue'
 import RelationManager from '../relation/RelationManager.vue'
@@ -39,6 +43,7 @@ const renderers = new Map<string, Component>([
   [RELATION_MANAGER, RelationManager],
   ['widget', WidgetField],
   ['partial', PartialField],
+  ['fileupload', FileuploadField],
 ])
 
 /** Types whose control shows the label itself (toggle cards, relation manager). */
@@ -51,13 +56,13 @@ const selfLabelled = new Set<string>(['switch', 'checkbox', RELATION_MANAGER])
 const recordBound = new Set<string>([RELATION_MANAGER])
 
 /** Types that hold no form value: never part of the save body (D-09). */
-const valueless = new Set<string>([RELATION_MANAGER, 'widget', 'partial'])
+const valueless = new Set<string>([RELATION_MANAGER, 'widget', 'partial', 'fileupload'])
 
 /**
  * Types whose control is a group rather than one focusable element: the
  * visible label is a span the group points at, not a label for an input.
  */
-const groupLabelledTypes = new Set<string>(['widget', 'partial'])
+const groupLabelledTypes = new Set<string>(['widget', 'partial', 'fileupload'])
 
 export function rendererFor(type: string): Component {
   return renderers.get(type) ?? UnsupportedField