feat(border): support decimal border widths and radii

[usmanvrtx]

Description

This PR adds support for decimal values in border widths and border radii across Ensemble widgets and themes.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)

What Has Changed

• Changed border width handling from int to double.
• Added decimal border width support for containers, forms, checkboxes, shapes, and themes.
• Added decimal border radius support.
• Added parsing for decimal border radius values from YAML strings.
• Added the stringToDoubles utility with minimum and maximum value validation.
• Preserved existing integer border values and behavior.

How to Test

1. Run flutter analyze from modules/ensemble.
2. Run flutter test from modules/ensemble.
3. Test decimal border widths:

Column:
  styles:
    borderWidth: 1.5
    borderColor: 0xff276ef1