test: add comprehensive tests for settings dialog components

Add component tests for ImportExportSection and SettingsDialog with full coverage of UI interactions, state management, and async workflows.

ImportExportSection.test.tsx (5 tests):
- Verify button states based on file selection
- Test import/export/clear interactions
- Validate loading, success, and error UI states

SettingsDialog.test.tsx (5 tests):
- Test loading state rendering
- Verify tab navigation and child component callbacks
- Validate save/cancel workflows with cleanup
- Test restart prompt and immediate restart flow
- Use Context Provider pattern to mock Tabs component
- Mock 7 child components for isolation

Test patterns demonstrated:
- Complex component isolation with deep mocking
- Context Provider mocking for UI library components
- Async workflow validation with waitFor
- Multi-hook mocking (useSettings + useImportExport)

All 45 tests passing (7 files, 1.13s execution time)

tests/components/ImportExportSection.test.tsx

@@ -0,0 +1,107 @@
+import { render, screen, fireEvent } from "@testing-library/react";
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { ImportExportSection } from "@/components/settings/ImportExportSection";
+
+const tMock = vi.fn((key: string) => key);
+
+vi.mock("react-i18next", () => ({
+  useTranslation: () => ({ t: tMock }),
+}));
+
+describe("ImportExportSection Component", () => {
+  const baseProps = {
+    status: "idle" as const,
+    selectedFile: "",
+    errorMessage: null,
+    backupId: null,
+    isImporting: false,
+    onSelectFile: vi.fn(),
+    onImport: vi.fn(),
+    onExport: vi.fn(),
+    onClear: vi.fn(),
+  };
+
+  beforeEach(() => {
+    tMock.mockImplementation((key: string) => key);
+    baseProps.onSelectFile.mockReset();
+    baseProps.onImport.mockReset();
+    baseProps.onExport.mockReset();
+    baseProps.onClear.mockReset();
+  });
+
+  it("should disable import button and show placeholder when no file selected", () => {
+    render(<ImportExportSection {...baseProps} />);
+
+    expect(screen.getByText("settings.noFileSelected")).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: "settings.import" })).toBeDisabled();
+    fireEvent.click(screen.getByRole("button", { name: "settings.exportConfig" }));
+    expect(baseProps.onExport).toHaveBeenCalledTimes(1);
+
+    fireEvent.click(screen.getByRole("button", { name: "settings.selectConfigFile" }));
+    expect(baseProps.onSelectFile).toHaveBeenCalledTimes(1);
+  });
+
+  it("should show filename and enable import/clear when file is selected", () => {
+    render(
+      <ImportExportSection
+        {...baseProps}
+        selectedFile={"/tmp/test/config.json"}
+      />,
+    );
+
+    expect(screen.getByText("config.json")).toBeInTheDocument();
+    const importButton = screen.getByRole("button", { name: "settings.import" });
+    expect(importButton).toBeEnabled();
+    fireEvent.click(importButton);
+    expect(baseProps.onImport).toHaveBeenCalledTimes(1);
+
+    fireEvent.click(screen.getByRole("button", { name: "common.clear" }));
+    expect(baseProps.onClear).toHaveBeenCalledTimes(1);
+  });
+
+  it("should show loading text and disable import button during import", () => {
+    render(
+      <ImportExportSection
+        {...baseProps}
+        selectedFile={"/tmp/test/config.json"}
+        isImporting
+        status="importing"
+      />,
+    );
+
+    const importingLabels = screen.getAllByText("settings.importing");
+    expect(importingLabels.length).toBeGreaterThanOrEqual(2);
+    expect(
+      screen.getByRole("button", { name: "settings.importing" }),
+    ).toBeDisabled();
+    expect(screen.getByText("common.loading")).toBeInTheDocument();
+  });
+
+  it("should display backup information on successful import", () => {
+    render(
+      <ImportExportSection
+        {...baseProps}
+        selectedFile={"/tmp/test/config.json"}
+        status="success"
+        backupId="backup-001"
+      />,
+    );
+
+    expect(screen.getByText("settings.importSuccess")).toBeInTheDocument();
+    expect(screen.getByText(/backup-001/)).toBeInTheDocument();
+    expect(screen.getByText("settings.autoReload")).toBeInTheDocument();
+  });
+
+  it("should display error message when import fails", () => {
+    render(
+      <ImportExportSection
+        {...baseProps}
+        status="error"
+        errorMessage="Parse failed"
+      />,
+    );
+
+    expect(screen.getByText("settings.importFailed")).toBeInTheDocument();
+    expect(screen.getByText("Parse failed")).toBeInTheDocument();
+  });
+});