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.

server/supabase/functions/_shared/billing-catalog.test.ts

@@ -2,6 +2,7 @@ import {
   createBillingCatalog,
   parseStripeCatalogPrice,
 } from './billing-catalog.ts'
+import { PLAN_PRICE_KRW } from './core-contract.generated.ts'
 
 function assert(condition: unknown, message: string): asserts condition {
   if (!condition) throw new Error(message)
@@ -46,13 +47,18 @@ Deno.test('Stripe catalog rejects mismatched, inactive, free, malformed, and one
 
 Deno.test('catalog exposes only configured provider prices and never invents a fallback', () => {
   const catalog = createBillingCatalog({
-    payple: { pro: 9900, pro_plus: 29900 },
+    payple: { pro: PLAN_PRICE_KRW.pro, pro_plus: PLAN_PRICE_KRW.pro_plus },
     stripe: {
       pro: { unit_amount: 990, currency: 'USD', interval: 'month', interval_count: 1 },
     },
   })
   assert(catalog.plans[0].prices.length === 2, 'pro must expose two verified providers')
   assert(catalog.plans[1].prices.length === 1, 'pro plus must omit unavailable Stripe')
+  assert(
+    catalog.plans[0].prices[0].unit_amount === PLAN_PRICE_KRW.pro
+      && catalog.plans[1].prices[0].unit_amount === PLAN_PRICE_KRW.pro_plus,
+    'Payple prices must come from the core plan catalog',
+  )
 
   const unavailable = createBillingCatalog({})
   assert(unavailable.plans.every((plan) => plan.prices.length === 0), 'missing configuration must stay unavailable')