Expose apiPort via commndline

[niteshsinghal85]

Fixes #1472

Added support for configuring the Dev Proxy API port via the --api-port command-line option.
This allows users to dynamically set the API port at runtime instead of only through configuration files.

The change makes IProxyConfiguration.ApiPort settable and integrates the new option into the command-line parsing logic with a default value of 8897.

[waldekmastykarz]

Cool! We'll review in the next couple of days. Thanks!

[Copilot]

Pull request overview

This PR adds support for configuring the Dev Proxy API port via the --api-port command-line option, allowing users to dynamically set the API port at runtime instead of only through configuration files.

Key changes:

• Made IProxyConfiguration.ApiPort settable to support runtime configuration
• Added --api-port command-line option with a default value of 8897
• Integrated the new option into command-line parsing and application startup logic

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
DevProxy.Abstractions/Proxy/IProxyConfiguration.cs	Changed ApiPort property from read-only to settable to support runtime configuration
DevProxy/Commands/DevProxyCommand.cs	Added --api-port option definition with description and help text, and configuration logic to apply the parsed value
DevProxy/Commands/DevProxyConfigOptions.cs	Added ApiPort property and option registration for initial parsing
DevProxy/Program.cs	Updated Kestrel configuration to use the command-line option with fallback to configuration file

[Copilot]

The apiPortOption is missing a description and help name, unlike other options in this constructor. For consistency with other options like ipAddressOption and logLevelOption, consider adding Description and HelpName properties.

Suggested change

	var apiPortOption = new Option<int?>(DevProxyCommand.ApiPortOptionName);
	var apiPortOption = new Option<int?>(DevProxyCommand.ApiPortOptionName)
	{
	Description = "Port on which Dev Proxy exposes its API.",
	HelpName = "PORT"
	};