Add Mellat e-payment, videos/instructions CMS, and legacy domain lookup.

Store gateway credentials per business, initiate/verify Mellat at checkout, and resolve old CMS ids from domains in the migrate modal.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/PROJECT_CONTEXT.md

@@ -342,7 +342,16 @@ Base: `/tenants/:host/user-products`
 | PATCH | `/cart/items/:itemId` | Update cart item quantity |
 | DELETE | `/cart/items/:itemId` | Remove cart item |
 | DELETE | `/cart` | Clear cart |
-| POST | `/cart/checkout` | Place order from cart (requires `addressId` or `shippingAddress`) |
+| POST | `/cart/checkout` | Place order from cart (`addressId` or `shippingAddress` + `payment`). For `e_payment_gate`, also send absolute `returnUrl`; response includes `payment.redirect` for bank redirect |
+
+#### Payments (public bank callbacks + methods)
+
+| Method | Path | Description |
+|--------|------|-------------|
+| GET | `/payments/methods` | Enabled gateways for this business (no secrets). Also on `GET /tenants/:host` as `ePayment` |
+| POST/GET | `/payments/:gateway/callback` | Bank return URL (Mellat first). Verifies/settles, then 303 → `returnUrl?status=…` |
+
+Gateway credentials live in `businesses.settings.store.ePayment` (dashboard: Website → E-Payment). Adapter registry supports Mellat now; stubs reserved for `sep`, `snappay`, `digipay`, `zarinpal`.
 
 #### Orders
 
@@ -584,7 +593,7 @@ See `.env.example` for the full list. Key groups:
 |-------|-----------|
 | Database | `DATABASE_URL`, `POSTGRES_*` |
 | Redis | `REDIS_URL`, `REDIS_HOST`, `REDIS_PORT` |
-| API | `PORT` |
+| API | `PORT`, `API_PUBLIC_BASE_URL` (bank payment callbacks) |
 | JWT | `JWT_ACCESS_SECRET`, `JWT_REFRESH_SECRET`, `JWT_*_EXPIRES_IN` |
 | SMS | `SMS_ENABLED`, `SMS_GAMA_BASE_URL`, `SMS_GAMA_USERNAME`, `SMS_GAMA_PASSWORD`, `SMS_GAMA_SOURCE_SERVICE`, `SMS_PARTNERS` |
 | S3 | `S3_ENDPOINT`, `S3_BUCKET`, `S3_PUBLIC_URL`, `S3_ACCESS_KEY_ID`, `S3_SECRET_ACCESS_KEY` |
@@ -608,6 +617,7 @@ See `.env.example` for the full list. Key groups:
 - Product variation values (which options a product offers)
 - Store items / product variants (price, stock, SKU)
 - Shopping cart + checkout + orders (customer + admin)
+- Online e-payment (Mellat first; multi-gateway registry for SEP / Snapp Pay / DigiPay / Zarinpal)
 - Product technical info
 - Category variations & technical forms
 - Tenant resolution by domain