merge: merge color-heading-optimization into feat-init

- Add color contrast optimization and checking tools
- Add heading hierarchy guidelines and checker
- Resolve package-lock.json conflict (keeping feat-init version)

src/app/(marketing)/about/client.tsx

@@ -223,7 +223,7 @@ export function AboutClient() {
                     <span className="text-sm font-medium text-[#C41E3A]">{milestone.date}</span>
                   </div>
                   <div className="flex-1">
-                    <h4 className="font-semibold text-[#1A1A2E] mb-1">{milestone.title}</h4>
+                    <h3 className="font-semibold text-[#1A1A2E] mb-1">{milestone.title}</h3>
                     <p className="text-[#718096] text-sm">{milestone.description}</p>
                   </div>
                 </motion.div>

src/app/(marketing)/contact/page.tsx

@@ -183,7 +183,7 @@ export default function ContactPage() {
               `}
             >
               <div>
-                <h3 className="text-lg font-semibold text-[#1C1C1C] mb-6">联系方式</h3>
+                <h2 className="text-lg font-semibold text-[#1C1C1C] mb-6">联系方式</h2>
                 <div className="space-y-4" data-testid="contact-info">
                   <div className="flex items-start gap-4 group" data-testid="email-info">
                     <div className="w-10 h-10 bg-[#C41E3A] rounded-md flex items-center justify-center flex-shrink-0 transition-transform duration-200 group-hover:scale-105">
@@ -222,7 +222,7 @@ export default function ContactPage() {
               <div className="bg-[#FFFBF5] p-5 rounded-lg border border-[#E5E5E5]" data-testid="work-hours-card">
                 <div className="flex items-center gap-2 mb-3">
                   <Clock className="w-4 h-4 text-[#C41E3A]" />
-                  <h4 className="text-sm font-medium text-[#1C1C1C]">工作时间</h4>
+                  <h2 className="text-sm font-medium text-[#1C1C1C]">工作时间</h2>
                 </div>
                 <div className="space-y-1">
                   <div className="flex justify-between text-sm" data-testid="work-hours-row">
@@ -235,7 +235,7 @@ export default function ContactPage() {
               <div className="bg-[#FFFBF5] p-5 rounded-lg border border-[#E5E5E5]">
                 <div className="flex items-center gap-2 mb-3">
                   <HeadphonesIcon className="w-4 h-4 text-[#C41E3A]" />
-                  <h4 className="text-sm font-medium text-[#1C1C1C]">我们的承诺</h4>
+                  <h2 className="text-sm font-medium text-[#1C1C1C]">我们的承诺</h2>
                 </div>
                 <div className="space-y-3">
                   <div className="flex items-start gap-2">
@@ -262,7 +262,7 @@ export default function ContactPage() {
               `}
             >
               <div className="bg-[#F5F7FA] p-6 sm:p-8 rounded-lg border border-[#E2E8F0] flex-1 flex flex-col">
-                <h3 className="text-lg font-semibold text-[#1A1A2E] mb-6">发送消息</h3>
+                <h2 className="text-lg font-semibold text-[#1A1A2E] mb-6">发送消息</h2>
                 
                 {isSubmitted ? (
                   <div className="text-center py-12 flex-1 flex items-center justify-center">

src/app/globals.css

@@ -31,7 +31,7 @@
   --color-brand-primary-bg: #FEF2F4;
   
   /* 背景色系 - 宣纸白 */
-  --color-bg-primary: #FAFAFA;
+  --color-bg-primary: #FFFFFF;
   --color-bg-secondary: #FFFBF5;
   --color-bg-tertiary: #F5F5F5;
   --color-bg-hover: #EFEFEF;
@@ -39,8 +39,8 @@
   /* 文字色系 - 墨色层次 */
   --color-text-primary: #1C1C1C;
   --color-text-secondary: #3D3D3D;
-  --color-text-tertiary: #5C5C5C;
-  --color-text-muted: #8C8C8C;
+  --color-text-tertiary: #4A4A4A;
+  --color-text-muted: #6B6B6B;
   
   /* 边框色系 */
   --color-border-primary: #E5E5E5;

src/lib/color-contrast.ts

@@ -0,0 +1,63 @@
+interface ColorRGB {
+  r: number;
+  g: number;
+  b: number;
+}
+
+interface ContrastResult {
+  passes: boolean;
+  ratio: number;
+  requiredRatio: number;
+}
+
+function hexToRgb(hex: string): ColorRGB {
+  const cleanHex = hex.replace('#', '');
+  const r = parseInt(cleanHex.substring(0, 2), 16);
+  const g = parseInt(cleanHex.substring(2, 4), 16);
+  const b = parseInt(cleanHex.substring(4, 6), 16);
+  return { r, g, b };
+}
+
+function getLuminance(rgb: ColorRGB): number {
+  const { r, g, b } = rgb;
+  const a = [r, g, b].map(v => {
+    v /= 255;
+    return v <= 0.03928 ? v / 12.92 : Math.pow((v + 0.055) / 1.055, 2.4);
+  });
+  return a[0] * 0.2126 + a[1] * 0.7152 + a[2] * 0.0722;
+}
+
+export function calculateContrastRatio(foreground: string, background: string): number {
+  const fgRgb = hexToRgb(foreground);
+  const bgRgb = hexToRgb(background);
+  
+  const fgLuminance = getLuminance(fgRgb);
+  const bgLuminance = getLuminance(bgRgb);
+  
+  const lighter = Math.max(fgLuminance, bgLuminance);
+  const darker = Math.min(fgLuminance, bgLuminance);
+  
+  return (lighter + 0.05) / (darker + 0.05);
+}
+
+export function meetsWCAGStandard(
+  foreground: string,
+  background: string,
+  level: 'AA' | 'AAA',
+  textSize: 'normal' | 'large'
+): ContrastResult {
+  const ratio = calculateContrastRatio(foreground, background);
+  
+  let requiredRatio: number;
+  if (level === 'AA') {
+    requiredRatio = textSize === 'normal' ? 4.5 : 3;
+  } else {
+    requiredRatio = textSize === 'normal' ? 7 : 4.5;
+  }
+  
+  return {
+    passes: ratio >= requiredRatio,
+    ratio,
+    requiredRatio
+  };
+}