refactor(core): keep plan prices, cloud quotas and public URLs in one contract (WS-A)

Prices, quotas and site URLs were copied by hand into the edge functions,
admin, desktop and the landing site, and the copies disagreed (Payple billed
9,900/29,900 KRW, admin labels said 12,900/24,900 KRW and $9.9/$19.9, the
site said 2,900/8,900 KRW).

- packages/core/src/plan-catalog.ts is the single source for PLAN_PRICE_KRW
  (Free 0 / Pro 2,900 / Pro+ 8,900 a month) and PLAN_QUOTA.
- packages/core/src/web-urls.ts is the single source for the public origin,
  the /app web-app base path, SITE_URLS and billingUrl().
- Deno cannot bundle packages/core, so scripts/ci/sync-core-contract.mjs
  generates _shared/core-contract.generated.ts; `npm run contract:check`
  fails on drift (same pattern as version:sync).
- Payple checkout, renewal and webhook amount checks now bill the catalog
  price, so existing subscribers move to the new price at their next renewal.
  quota.ts, team-contract.ts and the tests read the generated values.
- Admin MRR/ARR is computed in KRW from the catalog; license labels, the
  release link and desktop PREMIUM_LLM limits derive from core; the site
  imports prices and quotas directly.

Policy: docs/REFACTOR_POLICY.md Wave 3, W3-1 and W3-2.

packages/core/src/web-urls.ts

@@ -0,0 +1,43 @@
+// packages/core/src/web-urls.ts
+// 공개 웹 주소 SSOT — 결제·법률·다운로드·초대 링크는 모두 여기서 만든다.
+//
+// 한 도메인 아래 두 앱이 있다.
+//   /            랜딩 사이트(site/, Cloudflare Pages)  — 다운로드, 법률 문서, 초대 수락
+//   /app/...     웹앱(apps/web, Next basePath '/app') — 로그인, 결제, 대시보드
+// 사이트 브리지 워커(server/cloudflare-site-bridge)가 /app 요청을 웹앱으로 보낸다.
+// Deno 쪽 사본은 plan-catalog.ts 와 같은 방식으로 생성된다. 이 파일도 순수 값만 둔다.
+
+import type { PaidPlanTier } from './plan-catalog'
+
+export const PUBLIC_SITE_ORIGIN = 'https://d3ro.chanpaca.net'
+
+/** apps/web 의 Next basePath. next.config 와 브리지 워커 라우팅이 이 값을 따른다. */
+export const WEB_APP_BASE_PATH = '/app'
+
+export const WEB_APP_URL = `${PUBLIC_SITE_ORIGIN}${WEB_APP_BASE_PATH}`
+
+export const SITE_URLS = {
+  home: `${PUBLIC_SITE_ORIGIN}/`,
+  download: `${PUBLIC_SITE_ORIGIN}/#download`,
+  privacy: `${PUBLIC_SITE_ORIGIN}/privacy/`,
+  terms: `${PUBLIC_SITE_ORIGIN}/terms/`,
+  deleteAccount: `${PUBLIC_SITE_ORIGIN}/delete-account/`,
+  acceptInvite: `${PUBLIC_SITE_ORIGIN}/accept-invite/`,
+} as const
+
+/** 결제 결과로 돌아올 때 붙는 쿼리. apps/web 결제 페이지가 읽는 이름과 같다. */
+export type BillingReturn = 'success' | 'canceled'
+
+/**
+ * 웹 결제 페이지 URL.
+ * - `tier`: 고를 요금제를 미리 선택한다.
+ * - `result`: 외부 결제(Stripe 등)에서 돌아올 때의 결과.
+ */
+export function billingUrl(options: { tier?: PaidPlanTier; result?: BillingReturn } = {}): string {
+  const params = new URLSearchParams()
+  if (options.tier) params.set('tier', options.tier)
+  if (options.result === 'success') params.set('success', '1')
+  if (options.result === 'canceled') params.set('canceled', '1')
+  const query = params.toString()
+  return `${WEB_APP_URL}/billing${query ? `?${query}` : ''}`
+}