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.

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

@@ -1,5 +1,6 @@
 export type BillingCatalogTier = 'pro' | 'pro_plus'
-export type BillingCatalogProvider = 'payple' | 'stripe'
+/** 웹 결제는 Payple(KRW) 하나다. 모바일은 Google Play 스토어 가격을 쓰고 이 카탈로그에 오지 않는다. */
+export type BillingCatalogProvider = 'payple'
 
 export interface BillingCatalogPrice {
   provider: BillingCatalogProvider
@@ -19,54 +20,8 @@ export interface BillingCatalogResponse {
   plans: BillingCatalogPlan[]
 }
 
-interface StripePriceRecord {
-  id?: unknown
-  active?: unknown
-  type?: unknown
-  unit_amount?: unknown
-  currency?: unknown
-  recurring?: {
-    interval?: unknown
-    interval_count?: unknown
-  } | null
-}
-
-const CURRENCY_PATTERN = /^[a-z]{3}$/
-const INTERVALS = new Set(['day', 'week', 'month', 'year'])
-
-export function parseStripeCatalogPrice(
-  value: unknown,
-  expectedId: string,
-): Omit<BillingCatalogPrice, 'provider'> | null {
-  if (!value || typeof value !== 'object' || Array.isArray(value)) return null
-  const price = value as StripePriceRecord
-  if (
-    price.id !== expectedId
-    || price.active !== true
-    || price.type !== 'recurring'
-    || !Number.isSafeInteger(price.unit_amount)
-    || (price.unit_amount as number) < 1
-    || typeof price.currency !== 'string'
-    || !CURRENCY_PATTERN.test(price.currency)
-    || !price.recurring
-    || typeof price.recurring.interval !== 'string'
-    || !INTERVALS.has(price.recurring.interval)
-    || !Number.isSafeInteger(price.recurring.interval_count)
-    || (price.recurring.interval_count as number) < 1
-    || (price.recurring.interval_count as number) > 12
-  ) return null
-
-  return {
-    unit_amount: price.unit_amount as number,
-    currency: price.currency.toUpperCase(),
-    interval: price.recurring.interval as BillingCatalogPrice['interval'],
-    interval_count: price.recurring.interval_count as number,
-  }
-}
-
 export function createBillingCatalog(input: {
   payple?: Record<BillingCatalogTier, number> | null
-  stripe?: Partial<Record<BillingCatalogTier, Omit<BillingCatalogPrice, 'provider'>>> | null
 }): BillingCatalogResponse {
   const tiers: BillingCatalogTier[] = ['pro', 'pro_plus']
   return {
@@ -83,8 +38,6 @@ export function createBillingCatalog(input: {
           interval_count: 1,
         })
       }
-      const stripePrice = input.stripe?.[tier]
-      if (stripePrice) prices.push({ provider: 'stripe', ...stripePrice })
       return { tier, prices }
     }),
   }