feat: add Playwright integration tests with coverage and log capture

- Added `@playwright/test` and `c8` dependencies.
- Configured Playwright in `playwright.config.js` to run the dashboard server.
- Added `test/playwright/dashboard.spec.js` to verify dashboard functionality (loading, auth, config) and capture console logs.
- Modified `src/dashboard.mjs` to support graceful shutdown via `/shutdown` endpoint (guarded by `NODE_V8_COVERAGE`) for coverage collection.
- Updated `package.json` with `test:playwright` and `test:playwright:coverage` scripts.
- Updated `.gitignore` to exclude coverage and test artifacts.
- Fixed `host` default value in `src/cli-parser.mjs`.

Co-authored-by: PR0M3TH3AN <[email protected]>

src/cli-parser.mjs

@@ -17,7 +17,7 @@ export function parseArgs(argv) {
     dryRun: false,
     force: false,
     port: DEFAULT_DASHBOARD_PORT,
-    host: null,
+    host: undefined,
     logDir: 'task-logs',
     ignoreLogs: false,
     id: null,