移除卡片四角装饰，主题切换改为深色/浅色分段按钮

Co-authored-by: Cursor <cursoragent@cursor.com>

static/css/tech.css

@@ -100,12 +100,11 @@
     box-shadow:0 0 20px var(--nav-active-glow),inset 0 1px 0 rgba(255,255,255,.15);
 }
 
-.theme-toggle{
-    border-radius:999px;
-    transition:box-shadow .2s,border-color .2s;
+.theme-switch-btn:hover{
+    color:var(--text-primary);
 }
-.theme-toggle:hover{
-    box-shadow:0 0 16px var(--nav-hover-glow);
+.theme-switch-btn.active{
+    box-shadow:0 0 12px var(--btn-glow);
 }
 
 .card{
@@ -120,13 +119,6 @@
 .card::after{
     animation:tech-shine 5s ease-in-out infinite;
 }
-.card-corner{
-    width:16px;height:16px;opacity:.55;
-    transition:opacity .25s,box-shadow .25s;
-}
-.card:hover .card-corner{opacity:.9;box-shadow:0 0 8px var(--accent)}
-.card-corner.tr{top:10px;right:10px;border-top:2px solid;border-right:2px solid}
-.card-corner.bl{bottom:10px;left:10px;border-bottom:2px solid;border-left:2px solid}
 .card h2{letter-spacing:.03em}
 .card h2:before{
     box-shadow:0 0 12px var(--accent),0 0 4px var(--accent-2);