feat: comprehensive UI/a11y/i18n fixes and pre-push quality test

- Fix ClientWrappers missing 'about' namespace (MISSING_MESSAGE error)
- Add system/light/dark theme toggle with prefers-color-scheme detection
- Rewrite 404 page with i18n, accessibility, and proper navigation
- Rewrite books page with Header/Footer, i18n, and semantic HTML
- Add i18n keys to About, Footer, and both locale files
- Fix dark mode contrast: text-stone-300/600 -> text-stone-400
- Replace raw hex bg-[#fdfcf8] with bg-stone-50 across all components
- Guard console.error in ChatWidget and manage/page behind NODE_ENV
- Add aria-label to admin login form
- Remove emoji from manage page password toggle
- Update stale dates in privacy-policy and legal-notice
- Fix ScrollFadeIn index->delay prop type error in books page
- Fix privacy-policy and legal-notice landmark structure
- Add pre-push-check.test.ts: 13-category static analysis
  (i18n parity, namespace coverage, key resolution, accessibility,
   email validation, hex colors, emojis, console guards, env docs, types)
- Add explicit i18n check step to CI workflow

app/legal-notice/page.tsx

@@ -29,7 +29,8 @@ export default function LegalNotice() {
   }, [locale]);
 
   return (
-    <div className="min-h-screen bg-[#fdfcf8] dark:bg-stone-950 transition-colors duration-500">
+    <>
+    <div className="min-h-screen bg-stone-50 dark:bg-stone-950 transition-colors duration-500">
       <Header />
       <main className="max-w-7xl mx-auto px-6 pt-40 pb-20">
 
@@ -116,7 +117,7 @@ export default function LegalNotice() {
                 <Clock className="text-liquid-purple" size={20} />
                 <div>
                   <p className="text-[10px] font-black uppercase tracking-widest text-stone-400">Last Review</p>
-                  <p className="font-bold text-stone-900 dark:text-stone-100 text-sm">February 15, 2025</p>
+                  <p className="font-bold text-stone-900 dark:text-stone-100 text-sm">May 14, 2025</p>
                 </div>
               </div>
               <p className="text-xs text-stone-500 leading-relaxed">
@@ -127,7 +128,8 @@ export default function LegalNotice() {
           </div>
         </div>
       </main>
+      </div>
       <Footer />
-    </div>
+    </>
   );
 }