PHP configuration panel in WordPress Studio

### What

It would be useful if WordPress Studio allowed users to configure common PHP settings directly from the app interface.

### Why

Some WordPress projects require changing PHP values such as max_input_vars, memory_limit, upload_max_filesize, post_max_size or max_execution_time.

For example, when working with large menus, WPML, ACF, page builders or complex plugin settings, WordPress may show an error like:

PHP Request Startup: Input variables exceeded 1000. To increase the limit change max_input_vars in php.ini.

### How

A dedicated section such as Site settings > PHP configuration would make this much easier. Users could view and edit common PHP values per site, and Studio could restart the environment automatically or show a clear notice when a restart is required.

This would reduce friction for developers working with real WordPress projects locally.

Start by tracing the existing Site settings UI and the local PHP environment configuration. Determine how common PHP values could be scoped per site, how changes would be validated, and how restart requirements are surfaced; done means users can view and edit the requested settings with a clear restart outcome.

Written by the indexing model from the issue text.