feat(payments): remove EFT/havale, Stripe-only checkout + Turkish locale

EFT/Havale was retired; Stripe is now the sole payment method. Remove the
EFT code surface (shared PaymentMethod "eft" + EftPaymentInput + eftReceiptUrl,
EFT_RECEIPT_REQUIRED error code, billing UI receipt/filter/label paths,
payments.service eft read paths). DB columns (eft_receipt_url, bank_account_id,
bank_accounts) are kept and marked @deprecated to preserve historical records
and avoid a destructive migration — same pattern as the retired iyzico column.

Faz 3 conversion lever: set locale "tr" on the Stripe Checkout session. The
audience is Turkish B2B and ~60% of sessions reached the foreign-language
hosted page but never started a payment intent (pure abandonment, not decline).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/api/src/database/schema/core.ts

@@ -184,7 +184,9 @@ export const userBrands = pgTable(
   ],
 );
 
-// ─── Bank Accounts (EFT/Havale destination accounts, one active at a time) ────
+// ─── Bank Accounts ───────────────────────────────────
+// @deprecated EFT/Havale was retired (Stripe is the sole payment method). Table
+// kept only to preserve historical FK integrity; no rows are created anymore.
 export const bankAccounts = pgTable(
   "bank_accounts",
   {
@@ -225,7 +227,9 @@ export const payments = pgTable(
     iyzicoPaymentId: text("iyzico_payment_id"),
     stripeSessionId: text("stripe_session_id"),
     stripePaymentIntentId: text("stripe_payment_intent_id"),
+    /** @deprecated EFT/Havale retired (Stripe-only). Kept for historical data. */
     bankAccountId: uuid("bank_account_id").references(() => bankAccounts.id),
+    /** @deprecated EFT/Havale retired (Stripe-only). Kept for historical data. */
     eftReceiptUrl: text("eft_receipt_url"),
     adminNote: text("admin_note"),
     createdAt: timestamp("created_at", { withTimezone: true }).defaultNow().notNull(),

apps/api/src/payments/payments.service.ts

@@ -16,9 +16,9 @@ export class PaymentsService {
   /**
    * Payment history for the billing page. Returns a curated projection — never
    * the raw row — so internal columns (adminNote, iyzicoPaymentId,
-   * bankAccountId, session/intent ids) are not leaked to the client. planName
-   * is joined from the subscription's plan; Stripe receipt availability is
-   * surfaced as a boolean rather than exposing the payment intent id.
+   * session/intent ids) are not leaked to the client. planName is joined from
+   * the subscription's plan; Stripe receipt availability is surfaced as a
+   * boolean rather than exposing the payment intent id.
    */
   async getMyPayments(userId: string) {
     const rows = await this.db
@@ -29,7 +29,6 @@ export class PaymentsService {
         status: payments.status,
         createdAt: payments.createdAt,
         planName: plans.name,
-        eftReceiptUrl: payments.eftReceiptUrl,
         stripePaymentIntentId: payments.stripePaymentIntentId,
       })
       .from(payments)
@@ -45,16 +44,15 @@ export class PaymentsService {
       status: row.status,
       createdAt: row.createdAt,
       planName: row.planName ?? null,
-      eftReceiptUrl: row.eftReceiptUrl ?? null,
       hasStripeReceipt:
         row.method === "stripe" && row.status === "completed" && !!row.stripePaymentIntentId,
     }));
   }
 
   /**
-   * Resolve a receipt URL for one of the current user's payments.
-   * EFT receipts are stored locally; Stripe receipts are fetched live from the
-   * payment intent's latest charge. Returns { url: null } when none exists.
+   * Resolve a receipt URL for one of the current user's payments. Stripe is the
+   * sole payment method; receipts are fetched live from the payment intent's
+   * latest charge. Returns { url: null } when none exists.
    */
   async getReceiptUrl(userId: string, paymentId: string): Promise<{ url: string | null }> {
     const [payment] = await this.db
@@ -67,10 +65,6 @@ export class PaymentsService {
       throw new NotFoundException("Payment not found");
     }
 
-    if (payment.eftReceiptUrl) {
-      return { url: payment.eftReceiptUrl };
-    }
-
     if (payment.method === "stripe" && payment.stripePaymentIntentId) {
       return { url: await this.stripeService.getReceiptUrl(payment.stripePaymentIntentId) };
     }

apps/api/src/payments/stripe/stripe.service.ts

@@ -143,6 +143,10 @@ export class StripeService {
 
     const session = await this.stripe.checkout.sessions.create({
       mode: "payment",
+      // Render Stripe's hosted page in Turkish. The audience is Turkish B2B; a
+      // foreign-language checkout is a known abandonment driver (~60% of sessions
+      // reached the page but never started a payment intent).
+      locale: "tr",
       payment_method_types: ["card"],
       customer_email: userEmail,
       line_items: [