feat: unify doctor title handling and enhance specialty selection

- Implemented a helper function `displayDoctorName` to prepend "دکتر" to doctor names for consistent display across the application.
- Updated various components (InviteDoctorModal, DashboardPage, DoctorDetailPage, DoctorsPage, etc.) to utilize the new helper for rendering doctor names.
- Modified the DoctorFormPage to automatically add the "دکتر" title in the UI without requiring user input.
- Fixed the EditSpecialtyPicker component to allow multiple specialty selections, resolving a UI bug where only one specialty could be selected at a time.
- Ensured that the backend strips the "دکتر" title from the name during pre-registration and doctor creation processes.
- Added tests for the new functionality, including checks for title handling and specialty selection logic.
- Updated API documentation to reflect changes in name handling and display logic.

docs/api/auth.md

@@ -589,7 +589,7 @@ Submit a pre-registration request (doctor or clinic). Public endpoint — no aut
 | Field | Type | Required | Notes |
 |-------|------|----------|-------|
 | `type` | string | ✅ | `independent_doctor` \| `doctor_with_clinic` \| `clinic_manager` |
-| `name` | string | ✅ | min 2 chars |
+| `name` | string | ✅ | min 2 chars. عنوان «دکتر» ابتدای نام (و پیشوندهای تکراری «دکتر دکتر …») هنگام ثبت حذف می‌شود؛ نام تمیز ذخیره و در نمایش دوباره «دکتر» افزوده می‌شود. |
 | `mobile` | string | ✅ | 10–15 chars |
 | `info` | string | ❌ | specialty, address, etc. |