test(e2e): adapt to v0.22 dialog + theme picker redesigns

The redesign rollup in this branch replaced the Add Playlist dialog's
2-level type × subtype tabs with a single flat 5-card radiogroup, and
replaced the Settings theme list with a compact segmented control whose
options are just "Light"/"Dark"/"System" (no "theme" suffix). E2E tests
that pinned to the old roles/labels failed in CI:

  - basic / xtream / stalker / self-hosted: getByRole('tab', ...) on
    "Add via file upload" / "Xtream" / "Stalker" — there are no tabs in
    the new dialog. Switched to getByRole('radio', { name: /M3U file/i })
    and friends, matched against the new radio labels.
  - settings: getByRole('radio', { name: 'System theme' }) — the new
    picker uses just "System". Scoped to the [data-test-id="select-theme"]
    radiogroup so it doesn't collide with the identically-labelled
    cover-size options below.

The Electron `clickDialogSegmentedOption` helper grew a radio-role lookup
as its primary path and keeps the old tab/button/legacy-selector
fallbacks so a future redesign won't break every fixture again. The
"M3U" parent category becomes a no-op (the new picker has no standalone
M3U tile — callers always specialise to M3U URL/file/text immediately
after, which is what we want anyway).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web-e2e/src/basic.e2e.ts

@@ -13,7 +13,8 @@ test('basic test', async ({ page }) => {
     await page.getByRole('button', { name: 'Add playlist' }).click();
     const dialog = page.locator('mat-dialog-container');
     await expect(dialog).toBeVisible();
-    await dialog.getByRole('tab', { name: 'Add via file upload' }).click();
+    // v0.22 redesign: tabs were replaced with a flat 5-card radio picker.
+    await dialog.getByRole('radio', { name: /M3U file/i }).click();
     await page.setInputFiles('input[type="file"]', fixturePath);
     const addButton = dialog.getByRole('button', {
         name: 'Add playlist',