[Bug] Bedrock: site url mismatch - home_url() should be site_url()

### Environment
- Plugin version: 4.0.3
- WordPress: 6.9
- PHP: 8.3
- Installation: Bedrock (Composer-based, WP core in `/wp` subdirectory)

### Problem

On Bedrock installations, the plugin fails to connect with error:
```
Site Url Guard Request Failed!: site url mismatch (HTTP 400)
```

### Root Cause

In `classes/services/client.php`, line 54:
```php
'site_url' => trailingslashit( home_url() ),
```

The plugin sends `home_url()` to the API, but the OAuth token contains `site_url()`.

On Bedrock setups:
- `home_url()` = `https://example.com/`
- `site_url()` = `https://example.com/wp/`

This causes a mismatch.

### Proposed Fix

Change line 54 from:
```php
'site_url' => trailingslashit( home_url() ),
```

To:
```php
'site_url' => trailingslashit( site_url() ),
```

### Impact

- **Bedrock installations**: Fixes the issue
- **Standard WordPress**: No impact (home_url = site_url)

### Tested

We applied this fix locally and confirmed it works.

Start at classes/services/client.php line 54 and compare the URL sent in the site_url request field with the URL stored in the OAuth token. Done means Bedrock installations send the /wp/ site URL without causing the site URL mismatch, while standard WordPress installations continue to work.

Written by the indexing model from the issue text.