Adding support for FrankenPHP logging

[kkozlik]

Add FrankenPHP logging support via frankenphp_log()

This PR adds a new PEAR Log handler that routes log messages through FrankenPHP's native frankenphp_log() function, allowing PHP applications running under FrankenPHP to emit log output directly into FrankenPHP's own logging pipeline.

What's changed

• New Log_Franken handler class that implements the standard PEAR Log interface
• Log level mapping between PEAR Log priorities and FrankenPHP log levels
• Throws a RuntimeException on initialization if frankenphp_log() is not available (i.e. outside of a FrankenPHP context), ensuring misconfiguration is caught early rather than silently producing no output

Why

When running PHP in FrankenPHP worker mode, error_log() and similar functions may not route output the way you'd expect. Using frankenphp_log() ensures that log messages are handled by FrankenPHP's Caddy-based logging system, respecting its formatting and routing configuration.

References

• FrankenPHP
• frankenphp_log() documentation