feat(analytics): implement total transparency suite and SEO metadata standardization

- Added global ScrollDepthTracker (25%, 50%, 75%, 100%)
- Implemented ProductEngagementTracker for deep product analytics
- Added field-level tracking to ContactForm and RequestQuoteForm
- Standardized SEO metadata (canonical, alternates, x-default) across all routes
- Created reusable TrackedLink and TrackedButton components for server components
- Fixed 'useAnalytics' hook error in Footer.tsx by adding 'use client'

app/[locale]/contact/page.tsx

@@ -26,8 +26,9 @@ export async function generateMetadata({ params }: ContactPageProps): Promise<Me
     alternates: {
       canonical: `${SITE_URL}/${locale}/contact`,
       languages: {
-        'de-DE': '/de/contact',
-        'en-US': '/en/contact',
+        de: `${SITE_URL}/de/contact`,
+        en: `${SITE_URL}/en/contact`,
+        'x-default': `${SITE_URL}/en/contact`,
       },
     },
     openGraph: {