Initial vitest setup

app/src/test/setup.ts

@@ -0,0 +1,30 @@
+import '@testing-library/jest-dom';
+import { vi } from 'vitest';
+
+// Mock window.API_BASE_URL
+Object.defineProperty(window, 'API_BASE_URL', {
+  value: 'http://localhost:8080/api/v1',
+  writable: true,
+});
+
+// Mock matchMedia - required for Mantine components
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: vi.fn().mockImplementation((query: string) => ({
+    matches: false,
+    media: query,
+    onchange: null,
+    addListener: vi.fn(), // deprecated
+    removeListener: vi.fn(), // deprecated
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    dispatchEvent: vi.fn(),
+  })),
+});
+
+// Mock ResizeObserver - sometimes needed for Mantine components
+global.ResizeObserver = vi.fn().mockImplementation(() => ({
+  observe: vi.fn(),
+  unobserve: vi.fn(),
+  disconnect: vi.fn(),
+}));