refactor: web-to-pixso → web-to-ppt 全面改名

- 目录 web-to-pixso/ → web-to-ppt/
- 所有代码引用：PIXSO → WEB_TO_PPT, webToPixso → webToPPT
- 数据格式：pixso-design-capture → web-to-ppt-capture
- CSS 选择器：__web_to_pixso_ → __web_to_ppt_
- README 重写，移除 Pixso 相关描述
- docs/web-to-pixso-mapping.md → docs/web-to-ppt-mapping.md

web-to-ppt/logo/icon128.svg

@@ -0,0 +1,27 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 128 128" width="128" height="128">
+  <defs>
+    <linearGradient id="grad1" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" style="stop-color:#00D2FF;stop-opacity:1" />
+      <stop offset="100%" style="stop-color:#7C3AED;stop-opacity:1" />
+    </linearGradient>
+  </defs>
+  
+  <!-- 背景圆 -->
+  <circle cx="64" cy="64" r="60" fill="url(#grad1)"/>
+  
+  <!-- 网页图标 -->
+  <rect x="24" y="32" width="80" height="60" rx="4" fill="#fff" opacity="0.95"/>
+  
+  <!-- 网页内容线 -->
+  <rect x="32" y="44" width="40" height="4" rx="2" fill="#00D2FF"/>
+  <rect x="32" y="54" width="64" height="3" rx="1.5" fill="#E2E8F0"/>
+  <rect x="32" y="62" width="56" height="3" rx="1.5" fill="#E2E8F0"/>
+  <rect x="32" y="70" width="48" height="3" rx="1.5" fill="#E2E8F0"/>
+  
+  <!-- 箭头 -->
+  <path d="M72 80 L88 96 L104 80" stroke="#fff" stroke-width="4" fill="none" stroke-linecap="round" stroke-linejoin="round"/>
+  
+  <!-- Pixso 标志 -->
+  <circle cx="96" cy="56" r="16" fill="#fff"/>
+  <text x="96" y="61" text-anchor="middle" font-size="14" font-weight="bold" fill="url(#grad1)">P</text>
+</svg>