feat: Add aggregated Web Vitals monitoring

[Dobrunia]

Description:

• Collect all 5 Core Web Vitals (LCP, FCP, TTFB, INP, CLS) and send a single Hawk event when at least one metric is rated "poor"
• Event context includes all metrics with values, ratings and deltas for full diagnostics
• checkWebVitals is a standalone utility with no catcher dependency — reports via callback, catcher owns the send logic
• Enabled via webVitals: true in catcher settings, requires web-vitals as a peer dependency