feat: add CSS color conversion helpers for MTextColor and bump version to 1.4.1

[mlightcad]

Summary:

• Add CSS color parsing utilities for #rgb, #rrggbb, rgb(...), and rgba(...) with clamping and normalization.
• Add MTextColor.toCssColor() and MTextColor.fromCssColor(...).
• Bump package version to 1.4.1.

Tests:

• Add unit tests covering hex, short-hex, rgb(...), rgba(...), and transparent handling.
• Verify toCssColor() returns hex for RGB colors and null for ACI-only colors.