feat: add privacy retention controls

app/account/page.tsx

@@ -1,7 +1,9 @@
 import { redirect } from "next/navigation";
 import { getSession } from "@/lib/auth";
+import { db } from "@/lib/db";
 
 export default async function Account({ searchParams }: { searchParams: Promise<{ error?: string; updated?: string }> }) {
   const user = await getSession(); if (!user) redirect("/login"); const query = await searchParams;
-  return <><h1>帳號設定</h1>{query.error && <p className="error">{query.error}</p>}{query.updated && <p>密碼已更新。</p>}<section className="card"><p className="meta">帳號：{user.username}</p><h2>變更密碼</h2><form action="/api/auth/password" method="post"><label>目前密碼<input name="currentPassword" type="password" autoComplete="current-password" required /></label><label>新密碼<input name="newPassword" type="password" autoComplete="new-password" minLength={10} required /></label><label>確認新密碼<input name="confirmPassword" type="password" autoComplete="new-password" minLength={10} required /></label><button>更新密碼</button></form></section></>;
+  const ownedSources = db.prepare("SELECT count(*) AS count FROM sources WHERE user_id=?").get(user.id) as { count: number };
+  return <><h1>帳號設定</h1>{query.error && <p className="error">{query.error}</p>}{query.updated && <p>密碼已更新。</p>}<section className="card"><p className="meta">帳號：{user.username}</p><h2>變更密碼</h2><form action="/api/auth/password" method="post"><label>目前密碼<input name="currentPassword" type="password" autoComplete="current-password" required /></label><label>新密碼<input name="newPassword" type="password" autoComplete="new-password" minLength={10} required /></label><label>確認新密碼<input name="confirmPassword" type="password" autoComplete="new-password" minLength={10} required /></label><button>更新密碼</button></form></section><section className="card"><h2>刪除帳號與個人資料</h2>{ownedSources.count ? <p className="error">你仍是 {ownedSources.count} 個來源的建立者。請先轉移建立者或刪除來源，才能刪除帳號。</p> : <form action="/api/auth/delete" method="post"><p className="meta">此操作會移除你的 Hub 帳號、你建立的貼文與個人資料，且無法復原。</p><label>目前密碼<input name="currentPassword" type="password" autoComplete="current-password" required /></label><label>輸入 DELETE 確認<input name="confirmation" required /></label><button className="danger">永久刪除帳號</button></form>}</section></>;
 }