feat: schema-driven form descriptor API and dynamic form rendering

- Add ui section to kindred-rd.yaml with category_picker (multi-stage),
  item_fields, field_groups, category_field_groups, and field_overrides
- Add UIConfig structs to Go schema parser with full YAML/JSON tags
- Add ValidateUI() to validate field references against property schemas
- Add ValuesByDomain() helper to auto-derive subcategory picker stages
- Implement GET /api/schemas/{name}/form endpoint that returns resolved
  form descriptor with field metadata, widget hints, and category picker
- Replace GET /api/schemas/{name}/properties route with /form
- Add FormDescriptor TypeScript types
- Create useFormDescriptor hook (replaces useCategories)
- Rewrite CreateItemPane to render all sections dynamically from descriptor
- Update CategoryPicker with multi-stage domain/subcategory selection
- Delete useCategories.ts (superseded by useFormDescriptor)

web/src/api/types.ts

@@ -248,6 +248,68 @@ export interface PropertyDef {
 
 export type PropertySchema = Record<string, PropertyDef>;
 
+// Form Descriptor (from GET /api/schemas/{name}/form)
+export interface FormFieldDescriptor {
+  name: string;
+  type: string;
+  widget?: string;
+  label: string;
+  required?: boolean;
+  default?: unknown;
+  unit?: string;
+  description?: string;
+  options?: string[];
+  currency?: string;
+  derived_from_category?: Record<string, string>;
+  search_endpoint?: string;
+}
+
+export interface FormFieldGroup {
+  key: string;
+  label: string;
+  order: number;
+  fields: FormFieldDescriptor[];
+}
+
+export interface CategoryPickerStage {
+  name: string;
+  label: string;
+  values?: Record<string, string>;
+  values_by_domain?: Record<string, Record<string, string>>;
+}
+
+export interface CategoryPickerDescriptor {
+  style: string;
+  stages: CategoryPickerStage[];
+}
+
+export interface ItemFieldDef {
+  type: string;
+  widget: string;
+  label: string;
+  required?: boolean;
+  default?: unknown;
+  options?: string[];
+  derived_from_category?: Record<string, string>;
+  search_endpoint?: string;
+}
+
+export interface FieldOverride {
+  widget?: string;
+  currency?: string;
+  options?: string[];
+}
+
+export interface FormDescriptor {
+  schema_name: string;
+  format: string;
+  category_picker?: CategoryPickerDescriptor;
+  item_fields?: Record<string, ItemFieldDef>;
+  field_groups?: FormFieldGroup[];
+  category_field_groups?: Record<string, FormFieldGroup[]>;
+  field_overrides?: Record<string, FieldOverride>;
+}
+
 // API Token
 export interface ApiToken {
   id: string;