refactor: align landing page and 404 with Calculate blueprint

- Hero: remove framer-motion, CSS stagger animations, glass pill CTA button, refined typography and scroll indicator
- Stats: remove framer-motion, Lucide icons, tighter glass cards with mono labels
- ToolsGrid: remove framer-motion, editorial section heading, 4-col xl grid
- ToolCard: replace framer-motion motion.Link with plain Link + CSS hover, compact layout (icon→title→desc→badges+arrow), ElementType icon prop
- Footer: remove framer-motion, matches sidebar footer style
- BackToTop: remove framer-motion, JS scroll progress bar (1px primary line), compact glass button
- not-found: remove framer-motion and shadcn Button, glass pill CTA, 120px mono 404, CSS stagger
- page.tsx: remove unnecessary 'use client' directive

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/BackToTop.tsx

@@ -1,76 +1,44 @@
 'use client';
 
-import { motion, useScroll, useSpring } from 'framer-motion';
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useRef } from 'react';
+import { ChevronUp } from 'lucide-react';
 
 export default function BackToTop() {
   const [isVisible, setIsVisible] = useState(false);
-  const { scrollYProgress } = useScroll();
-  const scaleX = useSpring(scrollYProgress, {
-    stiffness: 100,
-    damping: 30,
-    restDelta: 0.001,
-  });
+  const barRef = useRef<HTMLDivElement>(null);
 
   useEffect(() => {
-    const toggleVisibility = () => {
-      if (window.pageYOffset > 300) {
-        setIsVisible(true);
-      } else {
-        setIsVisible(false);
+    const onScroll = () => {
+      setIsVisible(window.scrollY > 300);
+      if (barRef.current) {
+        const el = document.documentElement;
+        const scrolled = el.scrollTop / (el.scrollHeight - el.clientHeight);
+        barRef.current.style.transform = `scaleX(${scrolled})`;
       }
     };
-
-    window.addEventListener('scroll', toggleVisibility);
-    return () => window.removeEventListener('scroll', toggleVisibility);
+    window.addEventListener('scroll', onScroll, { passive: true });
+    return () => window.removeEventListener('scroll', onScroll);
   }, []);
 
-  const scrollToTop = () => {
-    window.scrollTo({
-      top: 0,
-      behavior: 'smooth',
-    });
-  };
-
   return (
     <>
-      {/* Progress bar */}
-      <motion.div
-        className="fixed top-0 left-0 right-0 h-1 bg-gradient-to-r from-purple-500 to-cyan-500 transform origin-left z-50"
-        style={{ scaleX }}
+      {/* Scroll progress bar */}
+      <div
+        ref={barRef}
+        className="fixed top-0 left-0 right-0 h-px bg-primary z-50 origin-left"
+        style={{ transform: 'scaleX(0)', transition: 'transform 0.1s linear' }}
       />
 
       {/* Back to top button */}
       {isVisible && (
-        <motion.button
-          onClick={scrollToTop}
-          className="fixed bottom-8 right-8 p-4 rounded-full glass hover:bg-accent/50 text-purple-400 hover:text-purple-300 transition-colors shadow-lg z-40 group"
-          initial={{ opacity: 0, y: 20 }}
-          animate={{ opacity: 1, y: 0 }}
-          exit={{ opacity: 0, y: 20 }}
-          whileHover={{ scale: 1.1 }}
-          whileTap={{ scale: 0.9 }}
+        <button
+          onClick={() => window.scrollTo({ top: 0, behavior: 'smooth' })}
+          className="fixed bottom-6 right-6 w-8 h-8 glass rounded-lg flex items-center justify-center text-muted-foreground/40 hover:text-primary hover:border-primary/40 transition-all duration-200 z-40"
           aria-label="Back to top"
+          style={{ animation: 'fadeIn 0.2s ease-out both' }}
         >
-          <svg
-            className="w-6 h-6"
-            fill="none"
-            stroke="currentColor"
-            viewBox="0 0 24 24"
-          >
-            <path
-              strokeLinecap="round"
-              strokeLinejoin="round"
-              strokeWidth={2}
-              d="M5 10l7-7m0 0l7 7m-7-7v18"
-            />
-          </svg>
-
-          {/* Tooltip */}
-          <span className="absolute bottom-full right-0 mb-2 px-3 py-1 text-xs text-white bg-gray-900 rounded-lg opacity-0 group-hover:opacity-100 transition-opacity whitespace-nowrap">
-            Back to top
-          </span>
-        </motion.button>
+          <ChevronUp className="w-3.5 h-3.5" />
+        </button>
       )}
     </>
   );