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/components/Contact.tsx

@@ -114,7 +114,7 @@ const Contact = () => {
       }
     } catch (error) {
       if (process.env.NODE_ENV === 'development') {
-        console.error("Error sending email:", error);
+        if (process.env.NODE_ENV === "development") console.error("Error sending email:", error);
       }
       showEmailError(
         "Network error. Please check your connection and try again.",
@@ -155,7 +155,7 @@ const Contact = () => {
   return (
     <section
       id="contact"
-      className="py-16 sm:py-24 md:py-32 px-4 sm:px-6 bg-[#fdfcf8] dark:bg-stone-950 transition-colors duration-500"
+      className="py-16 sm:py-24 md:py-32 px-4 sm:px-6 bg-stone-50 dark:bg-stone-950 transition-colors duration-500"
     >
       <div className="max-w-7xl mx-auto">
         <div className="grid grid-cols-1 md:grid-cols-12 gap-4 sm:gap-6 md:gap-8">