feat: implement layout 3-tier container architecture, desktop screen token, Gate 8 no-escape rule, and clean dead code

refer_landing_page/app/lectures/page.tsx

@@ -6,7 +6,7 @@ export default function LecturesPage() {
   const olderSemesters = semesters.slice(3);
 
   return (
-    <div className="space-y-16 py-6">
+    <div className="container-content space-y-16 py-6">
       {/* Header */}
       <section className="space-y-3">
         <div className="flex items-center gap-3">