💄 style(ui): replace inline gradients with reusable pastel blur balls; improve dark mode

- Introduce a global CSS utility `with-pastel-balls` in `web/src/index.css`, rendering pastel “blur balls” via ::before with CSS variables (`--pb1..--pb4`, `--pb-opacity`, `--pb-blur`) for easy theming.
- Apply the utility to pricing header cards and skeletons:
  - `web/src/components/table/model-pricing/layout/header/PricingVendorIntro.jsx`
  - `web/src/components/table/model-pricing/layout/header/PricingVendorIntroSkeleton.jsx`
- Remove per-component inline `linear-gradient(...)` backgrounds and redundant absolute-positioned decoration nodes to reduce duplication.
- Dark mode:
  - Keep the same pastel palette (pink/lavender/mint/peach).
  - Increase visibility with `--pb-opacity: 0.36`, `--pb-blur: 65px`, and `mix-blend-mode: screen`.
- No functional logic changes; UI-only. Lint passes.

Affected files:
- web/src/index.css
- web/src/components/table/model-pricing/layout/header/PricingVendorIntro.jsx
- web/src/components/table/model-pricing/layout/header/PricingVendorIntroSkeleton.jsx

web/src/index.css

@@ -593,6 +593,60 @@ html:not(.dark) .blur-ball-teal {
   opacity: 0.2;
 }
 
+/* ==================== 卡片马卡龙模糊球（类封装） ==================== */
+/* 使用方式：给容器加上 with-pastel-balls 类即可，无需在 JSX 中插入额外节点 */
+.with-pastel-balls {
+  position: relative;
+  overflow: hidden;
+  /* 默认变量（明亮模式） */
+  --pb1: #ffd1dc;
+  /* 粉 */
+  --pb2: #e5d4ff;
+  /* 薰衣草 */
+  --pb3: #d1fff6;
+  /* 薄荷 */
+  --pb4: #ffe5d9;
+  /* 桃 */
+  --pb-opacity: 0.55;
+  --pb-blur: 60px;
+}
+
+.with-pastel-balls::before {
+  content: '';
+  position: absolute;
+  inset: 0;
+  pointer-events: none;
+  z-index: 0;
+  background:
+    radial-gradient(circle at -5% -10%, var(--pb1) 0%, transparent 60%),
+    radial-gradient(circle at 105% -10%, var(--pb2) 0%, transparent 55%),
+    radial-gradient(circle at 5% 110%, var(--pb3) 0%, transparent 55%),
+    radial-gradient(circle at 105% 110%, var(--pb4) 0%, transparent 50%);
+  filter: blur(var(--pb-blur));
+  opacity: var(--pb-opacity);
+  transform: translateZ(0);
+}
+
+/* 暗黑模式下更柔和的色彩和透明度 */
+html.dark .with-pastel-balls {
+  /* 使用与明亮模式一致的“刚才那组”马卡龙色，但整体更柔和 */
+  --pb1: #ffd1dc;
+  /* 粉 */
+  --pb2: #e5d4ff;
+  /* 薰衣草 */
+  --pb3: #d1fff6;
+  /* 薄荷 */
+  --pb4: #ffe5d9;
+  /* 桃 */
+  --pb-opacity: 0.36;
+  --pb-blur: 65px;
+}
+
+/* 暗黑模式下用更柔和的混合模式避免突兀的高亮 */
+html.dark .with-pastel-balls::before {
+  mix-blend-mode: screen;
+}
+
 /* ==================== 表格卡片滚动设置 ==================== */
 .table-scroll-card {
   display: flex;