test(03-01): add Wave 0 RED baseline stubs for all 7 requirements

- src/App.test.tsx: WIZD-02 step routing (3 stubs)
- src/components/wizard/BackendSelectionStep.test.tsx: WIZD-01, WIZD-04 (10 stubs)
- src/components/wizard/RemoteConfigStep.test.tsx: BACK-01, BACK-02, BACK-03 (8 stubs)
- src/components/wizard/StepIndicator.test.tsx: WIZD-03 (5 stubs)
- All 26 tests fail RED with descriptive 'not yet implemented' messages

src/App.test.tsx

@@ -0,0 +1,17 @@
+// @vitest-environment jsdom
+// Covers WIZD-02: App renders the correct step component for currentStep 0, 1, 2
+import { describe, it, expect } from 'vitest';
+
+describe('App — step routing', () => {
+  it('renders BackendSelectionStep when currentStep is 0', () => {
+    expect.fail('not yet implemented');
+  });
+
+  it('renders RemoteConfigStep when currentStep is 1', () => {
+    expect.fail('not yet implemented');
+  });
+
+  it('renders DeploymentStep when currentStep is 2', () => {
+    expect.fail('not yet implemented');
+  });
+});