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/not-found.tsx

@@ -4,10 +4,13 @@ import { ArrowLeft, Search } from "lucide-react";
 import Link from "next/link";
 import { useRouter } from "next/navigation";
 import { useEffect, useState } from "react";
+import { useLocale, useTranslations } from "next-intl";
 
 export default function NotFound() {
   const [mounted, setMounted] = useState(false);
   const router = useRouter();
+  const locale = useLocale();
+  const t = useTranslations("notFound");
 
   useEffect(() => {
     setMounted(true);
@@ -16,7 +19,7 @@ export default function NotFound() {
   if (!mounted) return null;
 
   return (
-    <main className="min-h-screen bg-[#fdfcf8] dark:bg-stone-950 py-16 sm:py-20 md:py-24 px-4 sm:px-6 flex items-center justify-center transition-colors duration-500">
+    <main className="min-h-screen bg-stone-50 dark:bg-stone-950 py-16 sm:py-20 md:py-24 px-4 sm:px-6 flex items-center justify-center transition-colors duration-500">
       <div className="max-w-7xl mx-auto w-full">
         <div className="grid grid-cols-1 md:grid-cols-12 gap-4 sm:gap-6 md:gap-8 max-w-5xl mx-auto">
 
@@ -26,28 +29,30 @@ export default function NotFound() {
                 <div className="w-10 h-10 rounded-2xl bg-stone-900 dark:bg-stone-50 flex items-center justify-center text-white dark:text-stone-900 font-black text-xs">
                   404
                 </div>
-                <span className="text-[10px] font-black uppercase tracking-[0.3em] text-stone-400">Error Report</span>
+                <span className="text-[10px] font-black uppercase tracking-[0.3em] text-stone-400">{t("errorReport")}</span>
               </div>
               <h1 className="text-4xl sm:text-5xl md:text-8xl font-black tracking-tighter uppercase text-stone-900 dark:text-stone-50 leading-[0.85] mb-4 sm:mb-6 md:mb-8">
-                Page not <br/>Found<span className="text-liquid-mint">.</span>
+                {t("title").split(" ").map((word, i) => (
+                  <span key={i}>{i > 0 ? " " : ""}{word}{i === 0 ? "" : ""}{i === t("title").split(" ").length - 1 ? <span className="text-emerald-600 dark:text-emerald-400">.</span> : ""}</span>
+                ))}
               </h1>
-              <p className="text-base sm:text-lg md:text-xl lg:text-2xl font-light text-stone-500 max-w-md leading-relaxed">
-                The content you are looking for has been moved, deleted, or never existed.
+              <p className="text-base sm:text-lg md:text-xl lg:text-2xl font-light text-stone-500 dark:text-stone-400 max-w-md leading-relaxed">
+                {t("description")}
               </p>
             </div>
 
             <div className="mt-8 sm:mt-10 md:mt-12 flex flex-wrap gap-3 sm:gap-4">
               <Link
-                href="/en"
+                href={`/${locale}`}
                 className="group relative px-6 sm:px-10 py-3 sm:py-4 bg-stone-900 dark:bg-stone-50 text-white dark:text-stone-900 rounded-xl sm:rounded-2xl font-black text-xs uppercase tracking-[0.2em] shadow-xl hover:scale-105 transition-all"
               >
-                Return Home
+                {t("returnHome")}
               </Link>
               <button
                 onClick={() => router.back()}
                 className="px-6 sm:px-10 py-3 sm:py-4 bg-white dark:bg-stone-800 text-stone-900 dark:text-stone-100 border border-stone-200 dark:border-stone-700 rounded-xl sm:rounded-2xl font-black text-xs uppercase tracking-[0.2em] hover:bg-stone-50 dark:hover:bg-stone-700 transition-all"
               >
-                Go Back
+                {t("goBack")}
               </button>
             </div>
           </div>
@@ -55,14 +60,14 @@ export default function NotFound() {
           <div className="md:col-span-12 bg-stone-900 rounded-2xl sm:rounded-[2.5rem] p-6 sm:p-8 md:p-10 border border-stone-800 shadow-2xl text-white relative overflow-hidden group flex flex-col justify-between min-h-[200px]">
             <div className="relative z-10">
               <Search className="text-liquid-mint mb-4 sm:mb-6" size={28} />
-              <h3 className="text-xl sm:text-2xl font-black uppercase tracking-tighter mb-1 sm:mb-2">Explore Work</h3>
-              <p className="text-stone-400 text-sm font-medium">Maybe what you need is in my project archive?</p>
+              <h3 className="text-xl sm:text-2xl font-black uppercase tracking-tighter mb-1 sm:mb-2">{t("exploreWork")}</h3>
+              <p className="text-stone-400 text-sm font-medium">{t("exploreWorkDesc")}</p>
             </div>
             <Link
-              href="/en/projects"
+              href={`/${locale}/projects`}
               className="mt-5 sm:mt-8 inline-flex items-center gap-2 text-[10px] font-black uppercase tracking-widest text-liquid-mint group-hover:gap-4 transition-all"
             >
-              View Projects <ArrowLeft className="rotate-180" size={14} />
+              {t("viewProjects")} <ArrowLeft className="rotate-180" size={14} />
             </Link>
             <div className="absolute top-0 right-0 w-32 h-32 bg-liquid-mint/5 blur-3xl rounded-full -mr-16 -mt-16" />
           </div>