refactor(billing): remove Stripe; payments are Payple (web) and Google Play (mobile)

Stripe is not used. Keeping its checkout, portal and webhook paths meant a
second payment provider, a second return-URL format and dead UI.

- Delete the stripe-checkout, stripe-portal and stripe-webhook functions and
  their config; billing-catalog serves Payple prices only, and the web parser
  rejects a catalog that still mixes in Stripe prices.
- Web: drop the Stripe checkout/portal buttons, provider toggle and return
  notices; billing shows Payple only. Past rows with provider='stripe' are
  still displayed ("Stripe (종료)") with a support contact instead of a portal.
- Desktop: delete the Stripe checkout modal, payment IPC channels, preload
  namespace and their types; "Remove ads with Pro" opens the web billing page
  via license.openBilling. Support/refund copy names Payple.
- billingUrl() loses the Stripe-only success/canceled result option; the
  Deno contract is regenerated.
- Migrations and the DB's accepted provider values are untouched (history).
- Docs and the backlog record the removal (MON-04, EXT-STRIPE-01, GAP-BILL-03).

Verified: typecheck (desktop/web/admin/api-client/mobile), contract:check,
deno check all functions, deno test 80/80, desktop 1478/1480 on the Electron
runtime (2 known environment failures), web and admin builds, release
metadata and mobile boundary self-tests, eslint on changed files.

docs/map/10-feature-catalog.md

@@ -143,7 +143,7 @@ Status quick-reference: `[x]` done+verified · `[~]` partial/unverified · `[ ]`
 | MON-01 | Tier gating (Free/Pro/Pro+/Team/Enterprise) | [x] | [x] | [x] | [x] | `LicenseService`, entitlement provider |
 | MON-02 | Usage quotas (daily_usage) | [x] | [x] | [x] | [x] | |
 | MON-03 | Desktop offline license (Ed25519) | [x] | [-] | [-] | [x] | `crypto-license` + admin issuer |
-| MON-04 | Web checkout (Stripe) | [-] | [x] | [~] | [x] | Stripe checkout/portal/webhook |
+| MON-04 | ~~Web checkout (Stripe)~~ — **삭제됨 2026-09-26** | [-] | [-] | [-] | [-] | 사용자 결정: 결제는 웹 Payple(KRW) + 모바일 Google Play만. `stripe-checkout`/`stripe-portal`/`stripe-webhook` 함수, 웹 `checkout-button`/`portal-button`, 데스크톱 `CheckoutModal`·`payment-handlers`·`payment:*` IPC 삭제. 과거 `provider='stripe'` 구독 행은 읽기 전용 표시만(마이그레이션 불변). 운영 정리는 GAP-BILL-03 |
 | MON-05 | Web checkout (Payple) | [-] | [x] | [~] | [~] | Payple checkout/manage/renew/webhook; webhook signature pending |
 | MON-06 | Paywall / upgrade prompts | [x] | [x] | [x] | [x] | `UpgradePromptModal`, `ProPaywallScreen` |
 | MON-07 | Mobile IAP purchase + restore | [-] | [-] | [~] | [x] | `iap-verify` + `billing-context`; live store E2E blocked |
@@ -151,7 +151,7 @@ Status quick-reference: `[x]` done+verified · `[~]` partial/unverified · `[ ]`
 | MON-09 | Free-tier banner ads | [~] | [-] | [x] | [x] | Desktop adapters fail-closed; mobile AdMob test GREEN, prod serving blocked |
 | MON-10 | Rewarded ads → quota credits | [~] | [-] | [x] | [x] | Desktop `RewardedQuotaModal` (stub adapters); mobile SSV GREEN |
 | MON-11 | Ad mediation engine + settlement | [~] | [-] | [~] | [x] | Engine + settlement built. `DirectHouseSponsorAdapter` is now a **real configurable REST adapter** (bid/impression/click/reward via `endpointUrl`, fail-closed when unconfigured, unit-tested). Other 9 networks remain `UnavailableAdAdapter` stubs pending official SDKs. |
-| MON-12 | Subscription management (portal/store) | [-] | [x] | [x] | [x] | Stripe portal / Payple manage / Play manage |
+| MON-12 | Subscription management (portal/store) | [-] | [x] | [x] | [x] | Payple manage / Play manage (Stripe portal 삭제 2026-09-26) |
 
 ---