docs: update MkDocs palette toggle configuration

[j-d-ha]

Summary

Updates the MkDocs theme configuration to support automatic dark mode detection based on system preferences, along with improved palette toggle icons.

Changes

• Added automatic dark mode palette option that respects system prefers-color-scheme setting
• Updated toggle icons to use lightbulb variants for better visual consistency
• Added media queries to palette configurations for proper light/dark mode detection
• Removed navigation.tabs.sticky feature flag

Type of Change

• Documentation update
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Testing

• Verified MkDocs builds successfully with new configuration
• Tested automatic theme switching based on system preferences
• Confirmed manual theme toggle works correctly

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules