refactor(startup): simplify stack to Tauri-managed OpenFang + optional ChromeDriver

- Remove OpenFang CLI dependency from startup scripts
- OpenFang now bundled with Tauri and managed via gateway_start/gateway_status commands
- Add bootstrap screen in App.tsx to auto-start local gateway before UI loads
- Update Makefile: replace start-no-gateway with start-desktop-only
- Fix gateway config endpoints: use /api/config instead of /api/config/quick
- Add Playwright dependencies for future E2E testing

desktop/tests/e2e/playwright.config.ts

@@ -0,0 +1,27 @@
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './specs',
+  fullyParallel: true,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 2 : 0,
+  workers: process.env.CI ? 1 : undefined,
+  reporter: 'html',
+  use: {
+    baseURL: 'http://localhost:1420',
+    trace: 'on-first-retry',
+    screenshot: 'only-on-failure',
+    video: 'retain-on-failure',
+  },
+  projects: [
+    {
+      name: 'chromium',
+      use: { ...devices['Desktop Chrome'] },
+    },
+  ],
+  webServer: {
+    command: 'pnpm dev',
+    url: 'http://localhost:1420',
+    reuseExistingServer: true,
+  },
+});