UI 全面重设计: 明亮画廊风格 + 剧集合并显示

## 色彩体系重构
- tailwind.config.js: sand/ink 全新色阶 + shadow 阴影预设
- index.css: 全组件系统重写 (card/input/btn/badge/table)

## 核心页面重写
- LoginPage: 纯白卡片 + 品牌光晕 + Framer Motion 入场动画
- HomePage: Billboard 推荐位 + 剧集卡片联动媒体库
- Layout: 白色侧边栏 + 路由过渡动画
- MediaCard: 新增 linkTo prop, 悬停浮层优化

## 剧集合并显示
- LibraryPage: 使用 groupSeries 合并剧集, 分季选集详情
- 首页剧集卡片自动链接到媒体库详情

## 全量类名迁移 (43 文件)
- text-slate-* -> text-ink-*/text-sand-*
- text-primary-* -> text-brand-*
- text-white -> text-ink-600
- bg/border-slate-* -> bg/border-sand-*
- 500+ 深色硬编码类名清零

web/src/components/AppFooter.tsx

@@ -1,21 +1,9 @@
 import { Github, Globe, Send } from 'lucide-react'
 
 const LINKS = [
-  {
-    href: 'https://github.com/ShukeBta/MediaStationGo',
-    icon: Github,
-    label: '开源仓库',
-  },
-  {
-    href: 'https://github.com/ShukeBta',
-    icon: Globe,
-    label: '作者主页',
-  },
-  {
-    href: 'https://t.me/MediaStationGo',
-    icon: Send,
-    label: 'TG 群组',
-  },
+  { href: 'https://github.com/ShukeBta/MediaStationGo', icon: Github, label: '开源仓库' },
+  { href: 'https://github.com/ShukeBta', icon: Globe, label: '作者主页' },
+  { href: 'https://t.me/MediaStationGo', icon: Send, label: 'TG 群组' },
 ]
 
 export function AppFooter({ className = '' }: { className?: string }) {
@@ -23,12 +11,12 @@ export function AppFooter({ className = '' }: { className?: string }) {
     <footer className={`flex items-center justify-center gap-1 ${className}`}>
       {LINKS.map((link, i) => (
         <span key={link.href} className="flex items-center">
-          {i > 0 && <span className="mx-2 h-3 w-px bg-cream-900/20" />}
+          {i > 0 && <span className="mx-2 h-3 w-px bg-sand-300" />}
           <a
             href={link.href}
             target="_blank"
             rel="noopener noreferrer"
-            className="flex items-center gap-1.5 rounded-md px-2 py-1.5 text-xs text-cream-500 transition-colors hover:bg-cream-900/10 hover:text-cream-300"
+            className="flex items-center gap-1.5 rounded-lg px-2 py-1.5 text-xs text-sand-500 transition-colors hover:bg-sand-200 hover:text-ink-50"
             title={link.label}
           >
             <link.icon size={14} />