Feature: add Partner API - change client password

## New Partner Feature

### Partner API — Change Client Password

Partners can now reset or update any client's password programmatically via the Partner API — no manual UI access to the client account required.

#### New Endpoint

| Method | Endpoint | Description |
|--------|----------|-------------|
| `PUT` | `/partner/clients/change-password` | Change password by client email |

#### Request Body

```json
{
  "email": "string",
  "current_password": "string",
  "password": "string",
  "password_confirmation": "string"
}
```

| Field | Type | Description |
|-------|------|-------------|
| `email` | string | The client's account email address |
| `current_password` | string | The client's existing password |
| `password` | string | The new password to set |
| `password_confirmation` | string | Must match `password` |

#### Response Example

```json
{ "status": "ok" }
```

Error (400):
```json
{ "message": "Error message" }
```

#### What's New
- 🔐 **Change client passwords via Partner API** — update account credentials for any client by their email address
- 📦 No path parameters — all fields passed in the JSON request body
- ✅ Simple `{ "status": "ok" }` confirmation on success
- ⚠️ Requires knowledge of the client's `current_password` as a security check

#### How to Use
1. Authenticate with your **Partner API