feat(account): self-service deletion with a 7-day cooling-off period

Request signs out everywhere and freezes paid routes (423 + DB triggers);
signing in within 7 days shows the pending gate with 撤销注销. A periodic
idempotent worker purges personal content afterwards and keeps finance
rows against a tombstoned identity. Read-only admin list.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4f2nya58RoRu4yEmJgRGE

frontend/src/app/admin/account-deletions/page.tsx

@@ -0,0 +1,2 @@
+import AccountDeletionsResource from "@/components/admin/account-deletions-resource";
+export default function Page() { return <AccountDeletionsResource />; }