Add Google Analytics tracking (G-L8T0TB6M2C)

[urbantech]

Add GA4 tracking from ainative-website to builder.ainative.studio. Track all page views, generation events, signup conversions, and upgrade clicks. Same GA ID: G-L8T0TB6M2C.

[urbantech]

Already implemented and verified live. components/analytics/google-analytics.tsx loads gtag with G-L8T0TB6M2C (env-overridable via NEXT_PUBLIC_GA_ID), wired into app/layout.tsx. Confirmed live: production HTML at builder.ainative.studio includes both 'googletagmanager' and 'G-L8T0TB6M2C'. Tracking is active.