feat(layout): 重构布局组件体系与数据层

- 重构 Header 导航、Footer 页脚、MobileMenu 移动端菜单
- 新增 MobileTabBar 移动端底部导航栏
- 更新 MegaDropdown 大型下拉导航
- 重构 SEO 结构化数据组件
- 更新数据层常量 (products, services, solutions, navigation 等)
- 新增 useCountUp 数字递增 Hook
- 修复 .gitignore 中 src/lib 被错误忽略的问题

src/lib/constants/index.ts

@@ -9,5 +9,6 @@ export { NEWS, type NewsItem, type NewsCategory } from './news';
 export { TEAM_MEMBERS, type TeamMember } from './team';
 export { METHODOLOGY, type MethodologyPhase } from './methodology';
 export { SOLUTIONS, type Solution } from './solutions';
+export { CASE_STUDIES, CASE_INDUSTRIES, getCaseBySlug, getFeaturedCases, getCasesByIndustry, type CaseStudy, type CaseMetric, type CaseTimelinePhase, type CaseService, type CaseTestimonial } from './cases';
 export { HERO_THEMES, getHeroTheme, type HeroTheme, type HeroLayout, type HeroTexture } from './hero-themes';
 export { getProductCrossRefs, getSolutionCrossRefs, getServiceCrossRefs, type CrossReference } from './cross-references';