Add Media.Dropzone and Media.Preview as isolated elements

Introduce `Media.*` to modularize and customize file upload handling. Refactor media-related components to improve usability, add max item limits, overwrite support, and event callbacks.

app/src/ui/routes/test/index.tsx

@@ -11,6 +11,7 @@ import FlowFormTest from "../../routes/test/tests/flow-form-test";
 import ModalTest from "../../routes/test/tests/modal-test";
 import QueryJsonFormTest from "../../routes/test/tests/query-jsonform";
 import DropdownTest from "./tests/dropdown-test";
+import DropzoneElementTest from "./tests/dropzone-element-test";
 import EntityFieldsForm from "./tests/entity-fields-form";
 import FlowsTest from "./tests/flows-test";
 import JsonFormTest from "./tests/jsonform-test";
@@ -41,7 +42,8 @@ const tests = {
    AppShellAccordionsTest,
    SwaggerTest,
    SWRAndAPI,
-   SwrAndDataApi
+   SwrAndDataApi,
+   DropzoneElementTest
 } as const;
 
 export default function TestRoutes() {