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/package.json

@@ -58,6 +58,14 @@
       "types": "./src/utils/crypto-license.ts",
       "default": "./src/utils/crypto-license.ts"
     },
+    "./plan-catalog": {
+      "types": "./src/plan-catalog.ts",
+      "default": "./src/plan-catalog.ts"
+    },
+    "./web-urls": {
+      "types": "./src/web-urls.ts",
+      "default": "./src/web-urls.ts"
+    },
     "./supabase-config": {
       "types": "./src/supabase-config.ts",
       "default": "./src/supabase-config.ts"