feat(qs-viewer): use sun/moon svg icon for theme toggle

Author: vee1e

qs-viewer/src/App.tsx

@@ -391,8 +391,30 @@ const App: React.FC = () => {
         <div className="sidebar-header">
           <h1 className="app-title">FLOSS</h1>
           <div className="sidebar-header-buttons">
-            <button className="btn-ghost" onClick={() => setTheme(t => t === 'light' ? 'dark' : 'light')} title={theme === 'light' ? 'Switch to dark mode' : 'Switch to light mode'}>
-              {theme === 'light' ? 'Dark' : 'Light'}
+            <button
+              className="btn-ghost"
+              onClick={() => setTheme(t => t === 'light' ? 'dark' : 'light')}
+              title={theme === 'light' ? 'Switch to dark mode' : 'Switch to light mode'}
+              aria-label={theme === 'light' ? 'Switch to dark mode' : 'Switch to light mode'}
+              style={{ display: 'inline-flex', alignItems: 'center', justifyContent: 'center', width: 32, padding: '7px 0' }}
+            >
+              {theme === 'light' ? (
+                <svg viewBox="0 0 24 24" width="14" height="14" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+                  <path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z" />
+                </svg>
+              ) : (
+                <svg viewBox="0 0 24 24" width="14" height="14" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+                  <circle cx="12" cy="12" r="5" />
+                  <line x1="12" y1="1" x2="12" y2="3" />
+                  <line x1="12" y1="21" x2="12" y2="23" />
+                  <line x1="4.22" y1="4.22" x2="5.64" y2="5.64" />
+                  <line x1="18.36" y1="18.36" x2="19.78" y2="19.78" />
+                  <line x1="1" y1="12" x2="3" y2="12" />
+                  <line x1="21" y1="12" x2="23" y2="12" />
+                  <line x1="4.22" y1="19.78" x2="5.64" y2="18.36" />
+                  <line x1="18.36" y1="5.64" x2="19.78" y2="4.22" />
+                </svg>
+              )}
             </button>
             <button className="btn-ghost" onClick={handlePreview}>Preview</button>
             <label htmlFor="file-upload" className="btn-ghost" style={{ cursor: 'pointer' }}>