feat: enhance staff management and payment gateway features

- Fix national code handling in staff creation and updates to support Persian digits.
- Update ClinicStaff entity to allow longer national codes (up to 15 characters).
- Implement support for clinic secretaries in SecretaryController, allowing creation without a doctor UUID.
- Add a new endpoint to retrieve doctors associated with a clinic for secretary management.
- Improve appointment management by ensuring doctors are selectable even when no appointments exist.
- Extend PatientController to allow secretaries to create patient records if they have the appropriate permissions.
- Introduce a PriceInput component for better price formatting in forms, supporting Persian digits.
- Add a MockGateway for testing payment processes without real transactions.
- Enhance SMS settings management with an approval flow for post-visit text messages, including new fields for pending text and status.
- Update migrations to reflect changes in database schema for national codes and SMS settings.

docs/api/admin.md

@@ -775,7 +775,16 @@ Returns all site configuration values.
     "site_name": "ClinicPro",
     "support_phone": "",
     "max_cancel_hours_before": "24",
-    "appointment_reminder_hours": "2"
+    "appointment_reminder_hours": "2",
+    "payment_test_mode": "0",
+    "mellat_terminal_id": "",
+    "mellat_username": "",
+    "mellat_password": "",
+    "sep_terminal_id": "",
+    "sms_provider": "kavenegar",
+    "kavenegar_api_key": "",
+    "kavenegar_sender": "",
+    "sms_price_rials": "500"
   }
 }
 ```
@@ -791,7 +800,16 @@ Update one or more settings. Unknown keys are silently ignored.
 {
   "commission_enabled": "1",
   "commission_percent": "5",
-  "site_name": "کلینیک‌پرو"
+  "site_name": "کلینیک‌پرو",
+  "payment_test_mode": "1",
+  "mellat_terminal_id": "12345678",
+  "mellat_username": "user",
+  "mellat_password": "pass",
+  "sep_terminal_id": "87654321",
+  "sms_provider": "kavenegar",
+  "kavenegar_api_key": "your-api-key",
+  "kavenegar_sender": "10008664",
+  "sms_price_rials": "500"
 }
 ```
 
@@ -802,6 +820,15 @@ Update one or more settings. Unknown keys are silently ignored.
 - `commission_percent` — integer string, `0`–`100`
 - Commission applies only to regular users (`booked_by = user`); secretaries are exempt
 
+**Payment gateway rules:**
+- `payment_test_mode` — `"1"` = all payments use MockGateway (no real bank calls), `"0"` = real gateways
+- Gateway credentials (mellat/sep) read from DB first, fallback to env vars if DB value is empty
+- MockGateway callback: same URL pattern + `&mock=1&ResCode=0&RefId=MOCK-{orderId}`
+
+**SMS provider rules:**
+- `sms_provider` — `"kavenegar"` or `"rangineh"`
+- Kavenegar API key and sender read from DB first, fallback to env vars `KAVENEGAR_API_KEY`, `KAVENEGAR_SENDER`
+
 ---
 
 ## Pre-Registration Management