小程序端：设计系统收敛与排版层级修复

问题：88 个 wxss 里散落大量硬编码颜色/字号/字重，无法统一调整；
部分正文对比度不达 WCAG AA（4.5:1）；组件触摸目标偏小。

改动：
- 硬编码颜色收敛到语义 token（颜色统一走 design token，不再散落字面值）
- 修正全站字号阶梯：正文 ≥12px、角标 ≥11px；字重只用 400/500/600/700
- 组件触摸目标提升到 ≥44px，并补交互反馈
- 首页补氛围层次、强化排版层级

验证（本轮实测）：
- UI 契约门禁 18/18 PASS（含 wxml 结构、wxss 组件选择器、token 显式值断言）
- 声明级体检 88/88 通过（全部 wxss 声明合法）

交付物：artifacts/miniapp-design-v2-preview.html

miniapp/components/service-hero/index.wxss

@@ -1,63 +1,63 @@
 .service-hero {
-  position: relative;
-  height: 300rpx;
-  overflow: hidden;
-  border-radius: 0 0 32rpx 32rpx;
-  background: #fff4f7;
+  position:relative;
+  height:300rpx;
+  overflow:hidden;
+  border-radius:0 0 32rpx 32rpx;
+  background:var(--color-primary-light);
 }
 
 .service-hero__image,
 .service-hero__veil {
-  position: absolute;
-  inset: 0;
-  width: 100%;
-  height: 100%;
+  position:absolute;
+  inset:0;
+  width:100%;
+  height:100%;
 }
 
 .service-hero__veil {
-  background: linear-gradient(90deg, rgba(255, 250, 252, 0.98) 0%, rgba(255, 250, 252, 0.82) 38%, rgba(255, 250, 252, 0.08) 70%);
+  background:linear-gradient(90deg, rgba(255, 250, 252, 0.98) 0%, rgba(255, 250, 252, 0.82) 38%, rgba(255, 250, 252, 0.08) 70%);
 }
 
 .service-hero--night .service-hero__veil {
-  background: linear-gradient(90deg, rgba(18, 24, 83, 0.92) 0%, rgba(34, 31, 111, 0.64) 42%, rgba(34, 31, 111, 0.08) 72%);
+  background:linear-gradient(90deg, rgba(18, 24, 83, 0.92) 0%, rgba(34, 31, 111, 0.64) 42%, rgba(34, 31, 111, 0.08) 72%);
 }
 
 .service-hero__content {
-  position: relative;
-  z-index: 1;
-  display: flex;
-  flex-direction: column;
-  justify-content: center;
-  width: 54%;
-  height: 100%;
-  padding: 0 36rpx;
-  box-sizing: border-box;
+  position:relative;
+  z-index:1;
+  display:flex;
+  flex-direction:column;
+  justify-content:center;
+  width:54%;
+  height:100%;
+  padding:0 36rpx;
+  box-sizing:border-box;
 }
 
 .service-hero__eyebrow {
-  margin-bottom: 10rpx;
-  color: var(--color-primary);
-  font-size: 22rpx;
-  font-weight: 600;
-  letter-spacing: 2rpx;
+  margin-bottom:10rpx;
+  color:var(--color-primary-strong);
+  font-size:24rpx;
+  font-weight:600;
+  letter-spacing:2rpx;
 }
 
 .service-hero__title {
-  color: #24305e;
-  font-size: 40rpx;
-  font-weight: 700;
-  line-height: 1.28;
+  color:var(--color-text-strong);
+  font-size:40rpx;
+  font-weight:700;
+  line-height:1.28;
 }
 
 .service-hero__subtitle {
-  margin-top: 14rpx;
-  color: #737c96;
-  font-size: 24rpx;
-  line-height: 1.55;
+  margin-top:14rpx;
+  color:var(--color-text-tertiary);
+  font-size:24rpx;
+  line-height:1.55;
 }
 
 .service-hero--night .service-hero__eyebrow,
 .service-hero--night .service-hero__title,
 .service-hero--night .service-hero__subtitle {
-  color: #ffffff;
+  color:var(--color-text-inverse);
 }