feat: add back navigation link to Privacy Policy and ToS pages for improved user experience

apps/frontend/src/app/docs/privacy/page.tsx

@@ -3,6 +3,7 @@ import Link from "next/link";
 export default function PrivacyPage() {
     return (
         <div className="flex flex-col h-screen items-start justify-start p-6 max-w-[1000px] mx-auto">
+            <a href="/" className="text-sm text-foreground/80 hover:bg-accent">← Back</a>
             <h1 className="font-bold text-4xl">akiyama.mizuki.guru 개인정보 처리방침</h1>
             <p>제 1판</p>
             <p className="mt-4">

apps/frontend/src/app/docs/tos/page.tsx

@@ -1,6 +1,8 @@
 export default function ToS() {
     return (
         <div className="flex flex-col h-screen items-start justify-start p-6 max-w-[1000px] w-full mx-auto">
+            <a href="/" className="text-sm text-foreground/80 hover:bg-accent">← Back</a>
+
             <h1 className="font-bold text-4xl">akiyama.mizuki.guru 서비스 이용약관</h1>
             <p>제 1판</p>
             <h2 className="text-xl font-semibold mt-6" id="0">0. 서문</h2>