fix: 回退图标为现代化简洁风格

回退科技感设计，改为简洁美观风格：
- 柔和蓝色渐变背景（#4F8EF7 → #2563EB）
- 左上角微妙白色高光
- Georgia 衬线字体 MD 字母（白色带阴影）
- 底部半透明装饰线
- 圆角矩形，干净利落

icons.ico: 7 种尺寸（16~256px）
Icons.tsx AppIcon: SVG 版本同步更新

src/renderer/components/Icons.tsx

@@ -9,92 +9,30 @@ interface IconProps {
 
 const defaultProps: Partial<IconProps> = { size: 18 }
 
-// ===== 应用图标（科技感风格） =====
+// ===== 应用图标（现代化简洁风格） =====
 export function AppIcon({ size = 80 }: IconProps) {
-  const s = size
-  const margin = Math.max(1, s / 20)
-  const radius = Math.max(3, s / 5)
-  const gridStep = Math.max(4, s / 8)
-  const ringR = s / 3
-  const ringW = Math.max(1, s / 30)
-  const dotR = Math.max(1, s / 24)
-  const fontSize = Math.max(10, s * 45 / 100)
-  const arrowSize = Math.max(3, s / 7)
-  const arrowTop = s / 2 + Math.max(4, s / 8)
-  const arrowBottom = arrowTop + arrowSize
-  const lw = Math.max(1, s / 18)
-  const scanY = s - margin - Math.max(3, s / 10)
-  const scanLeft = margin + Math.max(3, s / 6)
-  const scanRight = s - margin - Math.max(3, s / 6)
-  const curX = s - margin - Math.max(3, s / 5)
-  const curY = margin + Math.max(3, s / 5)
-  const curSize = Math.max(2, s / 12)
-
   return (
-    <svg width={s} height={s} viewBox={`0 0 ${s} ${s}`} fill="none" xmlns="http://www.w3.org/2000/svg">
+    <svg width={size} height={size} viewBox="0 0 80 80" fill="none" xmlns="http://www.w3.org/2000/svg">
       <defs>
-        <linearGradient id="tech-bg" x1="0" y1="0" x2="0" y2="1">
+        <linearGradient id="app-bg" x1="0" y1="0" x2="0" y2="1">
-          <stop offset="0%" stopColor="#0F172A"/>
+          <stop offset="0%" stopColor="#4F8EF7"/>
-          <stop offset="100%" stopColor="#1E1B4B"/>
+          <stop offset="100%" stopColor="#2563EB"/>
+        </linearGradient>
+        <linearGradient id="app-highlight" x1="0" y1="0" x2="1" y2="1">
+          <stop offset="0%" stopColor="white" stopOpacity="0.15"/>
+          <stop offset="50%" stopColor="white" stopOpacity="0"/>
         </linearGradient>
-        <clipPath id="tech-clip">
-          <rect x={margin} y={margin} width={s - 2*margin} height={s - 2*margin} rx={radius}/>
-        </clipPath>
-        <filter id="tech-glow">
-          <feGaussianBlur stdDeviation="2" result="blur"/>
-          <feMerge>
-            <feMergeNode in="blur"/>
-            <feMergeNode in="SourceGraphic"/>
-          </feMerge>
-        </filter>
       </defs>
-
+      {/* 圆角矩形背景 */}
-      {/* 背景 */}
+      <rect x="4" y="4" width="72" height="72" rx="16" fill="url(#app-bg)"/>
-      <rect x={margin} y={margin} width={s - 2*margin} height={s - 2*margin} rx={radius} fill="url(#tech-bg)"/>
+      {/* 左上角高光 */}
-
+      <rect x="4" y="4" width="72" height="72" rx="16" fill="url(#app-highlight)"/>
-      <g clipPath="url(#tech-clip)">
+      {/* MD 文字 */}
-        {/* 科技网格 */}
+      <text x="40" y="44" textAnchor="middle" dominantBaseline="central"
-        {Array.from({length: Math.floor((s - 2*margin) / gridStep)}, (_, i) => {
+            fontFamily="Georgia, 'Times New Roman', serif" fontWeight="bold" fontSize="32"
-          const x = margin + (i + 1) * gridStep
+            fill="white" letterSpacing="2">MD</text>
-          return <line key={`gv${i}`} x1={x} y1={margin} x2={x} y2={s-margin} stroke="#3B82F6" strokeOpacity="0.08" strokeWidth="1"/>
+      {/* 底部装饰线 */}
-        })}
+      <rect x="20" y="58" width="40" height="2.5" rx="1.25" fill="white" fillOpacity="0.25"/>
-        {Array.from({length: Math.floor((s - 2*margin) / gridStep)}, (_, i) => {
-          const y = margin + (i + 1) * gridStep
-          return <line key={`gh${i}`} x1={margin} y1={y} x2={s-margin} y2={y} stroke="#3B82F6" strokeOpacity="0.08" strokeWidth="1"/>
-        })}
-
-        {/* 发光圆环 */}
-        <circle cx={s/2} cy={s/2} r={ringR + 2} fill="none" stroke="#3B82F6" strokeOpacity="0.15" strokeWidth="1"/>
-        <circle cx={s/2} cy={s/2} r={ringR} fill="none" stroke="#60A5FA" strokeOpacity="0.3" strokeWidth={ringW} filter="url(#tech-glow)"/>
-
-        {/* 四角光点 */}
-        {[[margin + radius/2, margin + radius/2], [s - margin - radius/2, margin + radius/2],
-          [margin + radius/2, s - margin - radius/2], [s - margin - radius/2, s - margin - radius/2]].map(([x, y], i) =>
-          <circle key={`dot${i}`} cx={x} cy={y} r={dotR} fill="#60A5FA" fillOpacity="0.6"/>
-        )}
-
-        {/* M 文字发光 */}
-        <text x={s/2} y={s/2 - Math.max(2, s/15)} textAnchor="middle" dominantBaseline="central"
-              fontFamily="system-ui, -apple-system, sans-serif" fontWeight="bold" fontSize={fontSize}
-              fill="#60A5FA" fillOpacity="0.2" filter="url(#tech-glow)">M</text>
-        {/* M 文字主体 */}
-        <text x={s/2} y={s/2 - Math.max(2, s/15)} textAnchor="middle" dominantBaseline="central"
-              fontFamily="system-ui, -apple-system, sans-serif" fontWeight="bold" fontSize={fontSize}
-              fill="#DCEBFF">M</text>
-
-        {/* ↓ 箭头 */}
-        <line x1={s/2} y1={arrowTop} x2={s/2} y2={arrowBottom} stroke="#93C5FD" strokeWidth={lw} strokeLinecap="round"/>
-        <line x1={s/2 - arrowSize/2} y1={arrowBottom - arrowSize/2} x2={s/2} y2={arrowBottom} stroke="#93C5FD" strokeWidth={lw} strokeLinecap="round"/>
-        <line x1={s/2 + arrowSize/2} y1={arrowBottom - arrowSize/2} x2={s/2} y2={arrowBottom} stroke="#93C5FD" strokeWidth={lw} strokeLinecap="round"/>
-
-        {/* 底部扫描线 */}
-        <line x1={scanLeft} y1={scanY} x2={scanRight} y2={scanY} stroke="#38BDF8" strokeOpacity="0.2" strokeWidth="2"/>
-        <line x1={scanLeft} y1={scanY + 2} x2={scanRight} y2={scanY + 2} stroke="#38BDF8" strokeOpacity="0.08" strokeWidth="1"/>
-
-        {/* 右上角光标 */}
-        <line x1={curX} y1={curY} x2={curX + curSize} y2={curY} stroke="#38BDF8" strokeOpacity="0.5" strokeWidth="1.5"/>
-        <line x1={curX + curSize} y1={curY} x2={curX + curSize} y2={curY + curSize} stroke="#38BDF8" strokeOpacity="0.5" strokeWidth="1.5"/>
-      </g>
     </svg>
   )
 }