feat(web): admin removeTrack API helper for M7 #372

DELETE /api/admin/tracks/{id} with optional ?unmonitor=true. Returns
the typed envelope with optional cascaded album/artist ids and the
lidarr_unmonitor_failed flag (only set on Lidarr-side failure when
unmonitor was requested — the file + DB delete still succeeded).
Caller invalidates TanStack Query keys for any vanished entities.

web/src/lib/api/admin/tracks.test.ts

@@ -0,0 +1,64 @@
+import { afterEach, describe, expect, test, vi } from 'vitest';
+import { removeTrack } from './tracks';
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+function stubFetch(status: number, body: unknown, init: Partial<Response> = {}) {
+  const res = new Response(
+    body === null ? null : JSON.stringify(body),
+    { status, headers: { 'Content-Type': 'application/json' }, ...init }
+  );
+  const spy = vi.fn().mockResolvedValue(res);
+  vi.stubGlobal('fetch', spy);
+  return spy;
+}
+
+describe('removeTrack', () => {
+  test('DELETEs /api/admin/tracks/:id with no query string when unmonitor unset', async () => {
+    const spy = stubFetch(200, {
+      deleted_track_id: 't-1',
+      deleted_album_id: 'al-1'
+    });
+
+    const r = await removeTrack('t-1');
+    expect(r.deleted_track_id).toBe('t-1');
+    expect(r.deleted_album_id).toBe('al-1');
+    expect(r.deleted_artist_id).toBeUndefined();
+    expect(r.lidarr_unmonitor_failed).toBeUndefined();
+
+    const call = spy.mock.calls[0];
+    expect(call[0]).toBe('/api/admin/tracks/t-1');
+    expect((call[1] as RequestInit).method).toBe('DELETE');
+  });
+
+  test('appends ?unmonitor=true when option set', async () => {
+    const spy = stubFetch(200, {
+      deleted_track_id: 't-1',
+      lidarr_unmonitor_failed: true
+    });
+
+    const r = await removeTrack('t-1', { unmonitor: true });
+    expect(r.lidarr_unmonitor_failed).toBe(true);
+
+    const call = spy.mock.calls[0];
+    expect(call[0]).toBe('/api/admin/tracks/t-1?unmonitor=true');
+  });
+
+  test('omits the query string when unmonitor: false', async () => {
+    const spy = stubFetch(200, { deleted_track_id: 't-1' });
+
+    await removeTrack('t-1', { unmonitor: false });
+    const call = spy.mock.calls[0];
+    expect(call[0]).toBe('/api/admin/tracks/t-1');
+  });
+
+  test('surfaces not_found as ApiError', async () => {
+    stubFetch(404, { error: 'not_found' });
+
+    await expect(removeTrack('t-1')).rejects.toMatchObject({
+      code: 'not_found'
+    });
+  });
+});