fix(theme): 品牌色令牌语义拆分与暗黑模式全站治理

- 拆分品牌色「文字/底色」双通道：新增 --color-brand-ink(-rgb)（深色 #F87171）
  与 tailwind brand.ink；text-brand → text-brand-ink 迁移 247 处；
  bg-brand/border-brand 保持 --color-brand-rgb 不翻转（红底白字 5.58:1 不能动）
- dark 块补齐 --color-brand-bg: #2A1418（修复深色白字压浅粉底 1.04:1）
- hero 徽章新增 --badge-accent-text 桥接：accentColor 直用作深底文字不可读
  （#1e3a5f 深底 1.65:1），浅色取原色 / 深色 color-mix 提亮
- 硬编码颜色 token 化：bg-white/text-gray-*/border-gray-* → bg-bg-*/text-text-*/border-border-*
- 可访问性：触控目标 <24px 归零（footer 链接列 [&_a]:min-h-6 收口 377 处等）、
  news 搜索框补 aria-label、标题跳级 h2→h4 修正为 h3、装饰 blur 光斑容器补
  overflow-hidden 消除伪文本裁剪
- 验证：tsc 0 / eslint 0 error / jest 0 失败用例 / dogfood 33 路由 × 双主题 P1-P3 全零

src/app/(marketing)/services/service-detail-content-v4.tsx

@@ -27,7 +27,7 @@ function DetailHero({ service }: { service: Service }) {
             <div className="block">{service.title}</div>
             <div className="block mt-4 sm:mt-6">
               <span className="relative inline-block">
-                <span className="relative text-brand font-black">
+                <span className="relative text-brand-ink font-black">
                   {firstBenefit}
                   <motion.span
                     className="absolute -bottom-2 left-0 w-full h-[3px] bg-brand"
@@ -57,7 +57,7 @@ function DetailHero({ service }: { service: Service }) {
             className="grid grid-cols-3 gap-8 mb-12 sm:mb-16 max-w-xl"
           >
             <div>
-              <div className="text-3xl sm:text-4xl font-black text-brand tracking-tight leading-none mb-2">
+              <div className="text-3xl sm:text-4xl font-black text-brand-ink tracking-tight leading-none mb-2">
                 10+
               </div>
               <div className="text-sm text-text-muted">人核心团队</div>
@@ -131,7 +131,7 @@ function OverviewSection({ service }: { service: Service }) {
                   key={i}
                   className="inline-flex items-center gap-2 px-4 py-2 text-sm border border-border-primary text-ink"
                 >
-                  <CheckCircle2 className="w-4 h-4 shrink-0 text-brand" />
+                  <CheckCircle2 className="w-4 h-4 shrink-0 text-brand-ink" />
                   <span className="font-medium">{benefit}</span>
                 </div>
               ))}
@@ -177,8 +177,8 @@ function FeaturesSection({ service }: { service: Service }) {
                 className="group relative p-8 sm:p-10 transition-all duration-150 hover:bg-bg-secondary hover:shadow-lg hover:-translate-y-1 bg-bg-primary"
               >
                 <div className="relative z-10">
-                  <Icon className="w-8 h-8 mb-6 text-brand" />
-                  <h3 className="text-lg sm:text-xl font-bold mb-3 text-ink group-hover:text-brand transition-colors duration-300">
+                  <Icon className="w-8 h-8 mb-6 text-brand-ink" />
+                  <h3 className="text-lg sm:text-xl font-bold mb-3 text-ink group-hover:text-brand-ink transition-colors duration-300">
                     {desc ? title : feature.slice(0, 10)}
                   </h3>
                   <p className="text-sm leading-relaxed text-text-secondary">
@@ -234,7 +234,7 @@ function ProcessSection({ service }: { service: Service }) {
                   className="w-2 h-2 rounded-full mb-6"
                   style={{ backgroundColor: index === 0 ? '#C41E3A' : 'var(--color-border-primary)' }}
                 />
-                <h3 className="text-lg font-bold mb-2 text-ink group-hover:text-brand transition-colors duration-300">
+                <h3 className="text-lg font-bold mb-2 text-ink group-hover:text-brand-ink transition-colors duration-300">
                   {desc ? title : step.slice(0, 6)}
                 </h3>
                 <p className="text-sm leading-relaxed text-text-secondary">