feat: 浏览量统计、浏览记录追踪、UI色彩优化

- 新增 Post.viewCount 字段，文章详情/列表/精选卡片显示浏览量
- 新增 PageView 模型记录访客IP(脱敏)、设备类型、来源
- 后台新增浏览记录独立页面及侧边栏菜单
- 仪表盘新增访问概览：页面访问/今日/独立IP/设备分布
- 整体色彩体系优化：降低黑白对比度、统一暖色调
- UI细节修复：focus-visible、Footer空列、mobile hover、transition-all等10+项

src/app/layout.tsx

@@ -1,6 +1,7 @@
 import type { Metadata } from "next";
 import Header from "@/components/Header";
 import Footer from "@/components/Footer";
+import TrackingProvider from "@/components/TrackingProvider";
 import { Noto_Serif_SC, Noto_Sans_SC, Cormorant_Garamond, Geist } from "next/font/google";
 import "./globals.css";
 import { cn } from "@/lib/utils";
@@ -81,7 +82,7 @@ export default function RootLayout({
         </a>
         <Header />
         <main id="main-content" className="flex-1">
-          {children}
+          <TrackingProvider>{children}</TrackingProvider>
         </main>
         <Footer />
       </body>