feat(downloads): local-upload UI — drag-drop dialog + progress (E7 S5c)

UploadDialog (drag-drop + native picker + optional display name) opened
from a new Upload button in the queue add-row. Uploads stream through a
new XHR helper (uploadReq in api/core) so the dialog shows real 0-100%
progress with a cancel — fetch/req can't report upload progress. The
upload lands as an already-done job; the S5b file-kind row gates it to
download+share. i18n HU/EN; upload cap/empty errors localize via the
shared structured-detail path.

frontend/src/components/UploadDialog.dom.test.tsx

@@ -0,0 +1,75 @@
+// @vitest-environment jsdom
+//
+// E7·S5c — the local-upload dialog. It's a general file upload (any type, no format list): a picked
+// file surfaces its name+size, and Upload streams it through api.uploadDownload (the XHR-progress
+// path). This drives the real dialog against a mocked api so we can assert the file + optional name
+// actually reach the ingest call, and that the success toast points at the library. i18n is
+// key-passthrough.
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { render, screen, fireEvent, waitFor, cleanup } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+const h = vi.hoisted(() => ({
+  uploadDownload: vi.fn(async (_f: File, _o: unknown) => ({ id: 42 })),
+  notify: vi.fn(),
+}));
+
+vi.mock("react-i18next", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("react-i18next")>();
+  return { ...actual, useTranslation: () => ({ t: (key: string) => key }) };
+});
+vi.mock("../lib/api", () => ({ api: { uploadDownload: h.uploadDownload } }));
+vi.mock("../lib/downloads", () => ({ invalidateDownloads: vi.fn() }));
+vi.mock("../lib/notifications", () => ({ notify: h.notify }));
+vi.mock("../lib/nav", () => ({ navigateTo: vi.fn() }));
+
+import UploadDialog from "./UploadDialog";
+
+const wrap = (onClose = vi.fn()) => {
+  const qc = new QueryClient();
+  return render(
+    <QueryClientProvider client={qc}>
+      <UploadDialog onClose={onClose} />
+    </QueryClientProvider>,
+  );
+};
+
+// The dialog portals into document.body, so query the whole document, not the render container.
+const fileInput = () => document.querySelector('input[type="file"]') as HTMLInputElement;
+
+beforeEach(() => {
+  h.uploadDownload.mockClear();
+  h.notify.mockClear();
+});
+afterEach(cleanup);
+
+describe("UploadDialog", () => {
+  it("shows the picked file's name and uploads it with the optional name", async () => {
+    const onClose = vi.fn();
+    wrap(onClose);
+    const f = new File(["hello world"], "notes.pdf", { type: "application/pdf" });
+    fireEvent.change(fileInput(), { target: { files: [f] } });
+
+    // The drop zone now surfaces the file name.
+    expect(screen.getByText("notes.pdf")).toBeTruthy();
+
+    // Optional display name.
+    const nameBox = screen.getByPlaceholderText("downloads.upload.namePlaceholder");
+    fireEvent.change(nameBox, { target: { value: "My notes" } });
+
+    fireEvent.click(screen.getByText("downloads.upload.submit"));
+
+    await waitFor(() => expect(h.uploadDownload).toHaveBeenCalledTimes(1));
+    const [passedFile, opts] = h.uploadDownload.mock.calls[0]!;
+    expect(passedFile).toBe(f);
+    expect((opts as { displayName?: string }).displayName).toBe("My notes");
+    await waitFor(() => expect(h.notify).toHaveBeenCalledTimes(1));
+    await waitFor(() => expect(onClose).toHaveBeenCalled());
+  });
+
+  it("keeps Upload disabled until a file is chosen", () => {
+    wrap();
+    const btn = screen.getByText("downloads.upload.submit").closest("button")!;
+    expect(btn.disabled).toBe(true);
+  });
+});