[2.x] add Amazon SES mail driver — core or FoF?

## Amazon SES Mail Driver

Amazon SES (Simple Email Service) is a popular choice for self-hosted Flarum installs running on AWS infrastructure. Symfony ships a first-party bridge (`symfony/amazon-mailer`) that would make implementation straightforward.

### What would be involved

- New composer dependency: `symfony/amazon-mailer`
- `src/Mail/SesDriver.php` implementing `DriverInterface`
- Settings: AWS access key, secret key, region
- `buildTransport()` via `SesApiAsyncAwsTransport` or `SesSmtpTransport`
- Locale keys, unit tests, integration test update

### Question: core or FoF?

Unlike Postmark (where the dep already exists), SES would require adding a new composer dependency to core. We're leaning towards a **Friends of Flarum extension** for this one — it keeps core lean and targets a more specific audience (AWS users).

Opinions welcome — particularly from anyone currently running Flarum on AWS.