feat: 科技感图标重新设计

应用图标（assets/icon.ico + icon.png）：
- 深色渐变背景（#0F172A 深海蓝 → #1E1B4B 深紫）
- 半透明科技网格线
- 蓝色发光圆环
- 四角蓝色光点装饰
- 带发光效果的白色 M 文字
- 蓝色渐变 ↓ 箭头
- 底部扫描线效果
- 右上角光标装饰
- 7 种尺寸（16~256px）

Icons.tsx AppIcon 同步更新：
- SVG 版本包含相同的科技感元素
- 使用 SVG filter 实现发光效果
- 使用 clipPath 实现圆角裁剪
- 使用 linearGradient 实现背景渐变

src/renderer/components/Icons.tsx

@@ -9,26 +9,92 @@ interface IconProps {
 
 const defaultProps: Partial<IconProps> = { size: 18 }
 
-// ===== 应用图标 =====
+// ===== 应用图标（科技感风格） =====
 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={size} height={size} viewBox="0 0 80 80" fill="none" xmlns="http://www.w3.org/2000/svg">
-      {/* 背景圆角矩形 */}
-      <rect x="4" y="4" width="72" height="72" rx="16" fill="url(#app-bg)" stroke="url(#app-stroke)" strokeWidth="2"/>
-      {/* Markdown M↓ 符号 */}
-      <path d="M22 28v24M22 52V40l8-8 8 8v12M46 28l6 12 6-12v24" stroke="white" strokeWidth="3.5" strokeLinecap="round" strokeLinejoin="round"/>
-      {/* 底部装饰线 */}
-      <rect x="16" y="60" width="48" height="3" rx="1.5" fill="rgba(255,255,255,0.3)"/>
+    <svg width={s} height={s} viewBox={`0 0 ${s} ${s}`} fill="none" xmlns="http://www.w3.org/2000/svg">
       <defs>
-        <linearGradient id="app-bg" x1="4" y1="4" x2="76" y2="76" gradientUnits="userSpaceOnUse">
-          <stop stopColor="#3B82F6"/>
-          <stop offset="1" stopColor="#1D4ED8"/>
-        </linearGradient>
-        <linearGradient id="app-stroke" x1="4" y1="4" x2="76" y2="76" gradientUnits="userSpaceOnUse">
-          <stop stopColor="#60A5FA"/>
-          <stop offset="1" stopColor="#2563EB"/>
+        <linearGradient id="tech-bg" x1="0" y1="0" x2="0" y2="1">
+          <stop offset="0%" stopColor="#0F172A"/>
+          <stop offset="100%" stopColor="#1E1B4B"/>
         </linearGradient>
+        <clipPath id="tech-clip">
+          <rect x={margin} y={margin} width={s - 2*margin} height={s - 2*margin} rx={radius}/>
+        </clipPath>
+        <filter id="tech-glow">
+          <feGaussianBlur stdDeviation="2" result="blur"/>
+          <feMerge>
+            <feMergeNode in="blur"/>
+            <feMergeNode in="SourceGraphic"/>
+          </feMerge>
+        </filter>
       </defs>
+
+      {/* 背景 */}
+      <rect x={margin} y={margin} width={s - 2*margin} height={s - 2*margin} rx={radius} fill="url(#tech-bg)"/>
+
+      <g clipPath="url(#tech-clip)">
+        {/* 科技网格 */}
+        {Array.from({length: Math.floor((s - 2*margin) / gridStep)}, (_, i) => {
+          const x = margin + (i + 1) * gridStep
+          return <line key={`gv${i}`} x1={x} y1={margin} x2={x} y2={s-margin} stroke="#3B82F6" strokeOpacity="0.08" strokeWidth="1"/>
+        })}
+        {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>
   )
 }