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/pages/PlayerPage.tsx

@@ -130,7 +130,7 @@ export function PlayerPage() {
     <div className="-m-6 flex min-h-screen flex-col bg-black md:-m-8">
       <button
         onClick={() => navigate(-1)}
-        className="absolute left-4 top-4 z-10 flex items-center gap-2 rounded-full bg-black/60 px-3 py-1.5 text-sm text-white backdrop-blur transition hover:bg-black/80"
+        className="absolute left-4 top-4 z-10 flex items-center gap-2 rounded-full bg-black/60 px-3 py-1.5 text-sm text-ink-600 backdrop-blur transition hover:bg-black/80"
       >
         <ArrowLeft size={16} /> 返回
       </button>
@@ -142,7 +142,7 @@ export function PlayerPage() {
           params.set('mode', next)
           setParams(params, { replace: true })
         }}
-        className="absolute right-4 top-4 z-10 flex items-center gap-2 rounded-full bg-black/60 px-3 py-1.5 text-sm text-white backdrop-blur transition hover:bg-black/80"
+        className="absolute right-4 top-4 z-10 flex items-center gap-2 rounded-full bg-black/60 px-3 py-1.5 text-sm text-ink-600 backdrop-blur transition hover:bg-black/80"
         title="切换播放模式"
       >
         {mode === 'hls' ? (
@@ -189,7 +189,7 @@ export function PlayerPage() {
             ))}
           </video>
         ) : (
-          <p className="text-slate-500">加载中…</p>
+          <p className="text-sand-500">加载中…</p>
         )}
       </div>
     </div>