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'

components/analytics/ScrollDepthTracker.tsx

@@ -0,0 +1,62 @@
+'use client';
+
+import { useEffect, useRef } from 'react';
+import { usePathname } from 'next/navigation';
+import { useAnalytics } from './useAnalytics';
+import { AnalyticsEvents } from './analytics-events';
+
+/**
+ * ScrollDepthTracker
+ * Tracks user scroll progress across pages.
+ * Fires events at 25%, 50%, 75%, and 100% depth.
+ */
+export default function ScrollDepthTracker() {
+  const pathname = usePathname();
+  const { trackEvent } = useAnalytics();
+  const trackedDepths = useRef<Set<number>>(new Set());
+
+  // Reset tracking when path changes
+  useEffect(() => {
+    trackedDepths.current.clear();
+  }, [pathname]);
+
+  useEffect(() => {
+    const handleScroll = () => {
+      const scrollY = window.scrollY;
+      const windowHeight = window.innerHeight;
+      const documentHeight = document.documentElement.scrollHeight;
+
+      // Calculate how far the user has scrolled in percentage
+      // documentHeight - windowHeight is the total scrollable distance
+      const totalScrollable = documentHeight - windowHeight;
+      if (totalScrollable <= 0) return; // Not scrollable
+
+      const scrollPercentage = Math.round((scrollY / totalScrollable) * 100);
+
+      // We only care about specific milestones
+      const milestones = [25, 50, 75, 100];
+
+      milestones.forEach((milestone) => {
+        if (scrollPercentage >= milestone && !trackedDepths.current.has(milestone)) {
+          trackedDepths.current.add(milestone);
+          trackEvent(AnalyticsEvents.SCROLL_DEPTH, {
+            depth: milestone,
+            path: pathname,
+          });
+        }
+      });
+    };
+
+    // Use passive listener for better performance
+    window.addEventListener('scroll', handleScroll, { passive: true });
+
+    // Initial check (in case page is short or already scrolled)
+    handleScroll();
+
+    return () => {
+      window.removeEventListener('scroll', handleScroll);
+    };
+  }, [pathname, trackEvent]);
+
+  return null;
+}