refactor：删除已弃用的组件和样式，迁移到 Tailwind CSS

- 改进项目页面、网站页面、友链页面
- 从 styles.css 中移除全局样式。
- 添加 tailwind.config.ts 以配置 Tailwind CSS。
- 更新 tsconfig.json，加入 Vue 组件的新路径映射。

app/components/PageSwitcher.vue

@@ -0,0 +1,51 @@
+<template>
+    <div class="my-4 mx-auto max-w-3xl w-full px-4 py-3 grid grid-cols-[auto_1fr_auto] gap-3 items-center">
+        <button :disabled="currentIndex <= 0" @click="goPrev"
+            class="bg-white/10 text-text-primary border border-white/15 rounded-2xl px-3 py-2 cursor-pointer transition-all duration-200 hover:bg-primary/20 hover:border-primary/40 hover:text-primary disabled:opacity-50 disabled:cursor-not-allowed">
+            上一页
+        </button>
+        <div class="flex gap-2 flex-wrap justify-center">
+            <button v-for="item in pages" :key="item.name" :class="{
+                'bg-primary/30 border-primary/60 text-primary shadow-lg shadow-primary/25':
+                    item.name === route.name,
+            }" @click="router.push({ name: item.name })"
+                class="px-2.5 py-2 bg-white/10 text-text-primary border border-white/15 rounded-2xl cursor-pointer transition-all duration-200 hover:bg-white/15 hover:border-primary/40">
+                {{ item.label }}
+            </button>
+        </div>
+        <button :disabled="currentIndex >= pages.length - 1" @click="goNext"
+            class="bg-white/10 text-text-primary border border-white/15 rounded-2xl px-3 py-2 cursor-pointer transition-all duration-200 hover:bg-primary/20 hover:border-primary/40 hover:text-primary disabled:opacity-50 disabled:cursor-not-allowed">
+            下一页
+        </button>
+    </div>
+</template>
+
+<script setup>
+import { computed } from "vue";
+import { useRoute, useRouter } from "vue-router";
+
+const router = useRouter();
+const route = useRoute();
+
+const pages = [
+    { name: "index", label: "首页" },
+    { name: "about", label: "关于" },
+    { name: "sites", label: "网站" },
+    { name: "projects", label: "项目" },
+    { name: "friends", label: "友链" },
+];
+
+const currentIndex = computed(() => pages.findIndex((item) => item.name === route.name));
+
+const goPrev = () => {
+    if (currentIndex.value > 0) {
+        router.push({ name: pages[currentIndex.value - 1].name });
+    }
+};
+
+const goNext = () => {
+    if (currentIndex.value < pages.length - 1) {
+        router.push({ name: pages[currentIndex.value + 1].name });
+    }
+};
+</script>