feat(Home): 首屏蒙层暗化方案A：叠加55%深蓝渐变蒙层，激活Canvas粒子网/光晕/4色轨道彗星全部显形，文字对比度增强

src/components/Home.tsx

@@ -174,7 +174,7 @@ function HeroParticleCanvas() {
       ref={ref}
       aria-hidden="true"
       className="absolute inset-0 w-full h-full pointer-events-none"
-      style={{ zIndex: 2 }}
+      style={{ zIndex: 3 }}
     />
   );
 }
@@ -231,13 +231,24 @@ export default function Home({ locale }: { locale: Locale }) {
           alt=""
           aria-hidden="true"
           className="absolute inset-0 w-full h-full object-cover"
-          style={{ zIndex: 0, opacity: 0.92 }}
+          style={{ zIndex: 0 }}
           loading="eager"
           decoding="async"
         />
 
+        {/* 方案A：半透明深色蒙层 → 让粒子/光晕从浅色背景中"显形"，同时增强左下白字对比度 */}
+        <div
+          aria-hidden="true"
+          className="absolute inset-0 pointer-events-none"
+          style={{
+            zIndex: 1,
+            background:
+              'linear-gradient(135deg, rgba(10, 14, 42, 0.62) 0%, rgba(20, 24, 47, 0.54) 50%, rgba(29, 33, 80, 0.50) 100%)',
+          }}
+        />
+
         {/* 雾化光晕 4 球（慢速漂浮，最底层之上但粒子网之下） */}
-        <div aria-hidden="true" className="absolute inset-0 pointer-events-none" style={{ zIndex: 1, overflow: 'hidden' }}>
+        <div aria-hidden="true" className="absolute inset-0 pointer-events-none" style={{ zIndex: 2, overflow: 'hidden' }}>
           {HERO_GLOW_ORBS.map((o, i) => (
             <span
               key={i}
@@ -254,11 +265,11 @@ export default function Home({ locale }: { locale: Locale }) {
           ))}
         </div>
 
-        {/* Canvas 全屏粒子 + 邻近连线（白/蓝/紫/粉 4 色） */}
+        {/* Canvas 全屏粒子 + 邻近连线（白/蓝/紫/粉 4 色），z-index:3 */}
         <HeroParticleCanvas />
 
         {/* 粒子层：环绕中央玻璃球的轨道粒子（7 圈 / 22 颗，4 色分色，linear 匀速环绕） */}
-        <div className="hero-orbit pointer-events-none" aria-hidden="true" style={{ left: '70%', top: '46%', zIndex: 3 }}>
+        <div className="hero-orbit pointer-events-none" aria-hidden="true" style={{ left: '70%', top: '46%', zIndex: 4 }}>
           {orbits.flatMap((o, i) =>
             o.dots.map((d, j) => {
               // 全局 dot 序号，用于 stagger 脉冲相位 + 颜色循环