[WIP] Add ability to save current configuration as a preset

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

---

This section details on the original issue you should resolve

<issue_title>[EPIC] Implement Preset Save Functionality</issue_title>
<issue_description>Add ability to save current configuration as a preset.

Objectives

• Add "Save as Preset" button
• Implement preset name dialog
• Save configuration to XML
• Store in user预设 directory

Linked Tasks

• Add "Save as Preset" to File menu
• Create preset name input dialog
• Implement XML serialization
• Create ~/.plugin_configurator/presets/ directory
• Add error handling

Success Criteria

• Presets save correctly to XML
• All settings included in saved file
• Directory created if doesn't exist
• Error handling works

Timeline

• Start: 2026-04-27
• End: 2026-04-30
• Duration: 4 days</issue_description>

Comments on the Issue (you are @copilot in this section)