Add reusable Bootstrap 5 autocomplete-with-create component and backend endpoint traits

[Copilot]

This PR introduces a reusable admin form component for searching entities via autocomplete and creating missing entries inline. It standardizes the backend JSON contract and wires a Bootstrap 5 UI/JS implementation that can be dropped into existing abstract form flows.

• Backend endpoint traits (search + create)

  • Added HasAutocompleteSearchTrait and HasAutocompleteCreateTrait under src/Library/Controllers/Traits/.
  • Exposes generic actions: autocompleteSearchAction() and autocompleteCreateAction().
  • Normalizes request params (q, limit, name by default), success/error payloads, duplicate handling hooks, and response formatting hooks.
  • Includes safe JSON encoding fallback for encoding failures.

• Reusable Bootstrap 5 field partial

  • Added resources/themes/bootstrap5/views/abstract/modules/item-form/fields/autocomplete_create.php.
  • Provides hidden ID input + visible search input + dropdown results + inline “create new” action.
  • Supports configurable URLs/methods/params/messages/limits and read-only/disabled/required behavior via view variables and data-* attributes.

• Frontend component integration

  • Added AutocompleteCreateComponent in resources/themes/bootstrap5/assets/scripts/admin/components/AutocompleteCreate.js.
  • Registered component in resources/themes/bootstrap5/assets/scripts/admin/app.js.
  • Implements debounced search, result rendering, keyboard navigation, selection sync (id/label), inline create, error feedback, and Turbo-safe cleanup/rebind behavior.

• Bootstrap 5 styling

  • Added resources/themes/bootstrap5/assets/sass/ui/_autocomplete-create.scss.
  • Imported in resources/themes/bootstrap5/assets/sass/ui/core.scss.
  • Styles dropdown/results/loading/empty/create-row states to align with existing Bootstrap 5 theme tokens.

• Tests + docs

  • Added trait-focused unit tests for empty query/name, normal success paths, duplicate conflict, and created response mapping.
  • Extended README with endpoint contract, trait extension points, and field usage expectations.

// Example: controller integration
class TagsController
{
    use \ByTIC\AdminBase\Library\Controllers\Traits\HasAutocompleteSearchTrait;
    use \ByTIC\AdminBase\Library\Controllers\Traits\HasAutocompleteCreateTrait;

    protected function autocompleteSearchFetchRecords(string $query, int $limit): iterable { /* ... */ }
    protected function autocompleteCreatePersistRecord(string $name): mixed { /* ... */ }
}