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/js/theme.js

@@ -1,16 +1,24 @@
 (function () {
     var KEY = 'qihuo-theme';
 
+    function updateButtons(theme) {
+        document.querySelectorAll('[data-theme-pick]').forEach(function (btn) {
+            var pick = btn.getAttribute('data-theme-pick');
+            var on = pick === theme;
+            btn.classList.toggle('active', on);
+            btn.setAttribute('aria-pressed', on ? 'true' : 'false');
+        });
+    }
+
     function apply(theme) {
+        if (theme !== 'light' && theme !== 'dark') {
+            theme = 'dark';
+        }
         document.documentElement.setAttribute('data-theme', theme);
         try {
             localStorage.setItem(KEY, theme);
         } catch (e) { /* ignore */ }
-        var btn = document.getElementById('theme-toggle');
-        if (btn) {
-            btn.setAttribute('data-active', theme);
-            btn.setAttribute('aria-label', theme === 'light' ? '切换到深色' : '切换到浅色');
-        }
+        updateButtons(theme);
     }
 
     var saved = null;
@@ -26,11 +34,12 @@
     }
 
     document.addEventListener('DOMContentLoaded', function () {
-        var btn = document.getElementById('theme-toggle');
-        if (!btn) return;
-        btn.addEventListener('click', function () {
-            var cur = document.documentElement.getAttribute('data-theme') || 'dark';
-            apply(cur === 'dark' ? 'light' : 'dark');
+        var cur = document.documentElement.getAttribute('data-theme') || 'dark';
+        updateButtons(cur);
+        document.querySelectorAll('[data-theme-pick]').forEach(function (btn) {
+            btn.addEventListener('click', function () {
+                apply(btn.getAttribute('data-theme-pick'));
+            });
         });
     });
 })();