Frontend test functionality was implemented but never committed to git.
Re-adds:
- profiles.js: testCard(), testForm(), _showTestResult(), test btn in renderCard
- api.js: testProfile(id) and probeConnectivity(body) methods
- index.html: 测试连通性 button + result div in profile form
- app.css: .btn-test and .profile-test-result styles
Backend /probe and /{id}/test endpoints were already present in llm_profiles.py.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>