feat(admin): add Select2 styling consistency and dynamic input binding

- Replace `Select2` Bootstrap 5 theme with custom overrides matching `form-select`
- Add comprehensive `Select2` styling for single/multiple selection states
- Support validation states (valid/invalid) with custom focus shadows
- Implement responsive sizing (sm/lg variants) for form consistency
- Add RTL language support for proper text direction handling
- Include dark mode compatibility and reduced motion accessibility
- Add generic input binding handler using data attributes only
- Support nested property paths (style.color, dataset.foo, etc.)
- Enable dynamic target updates without custom JavaScript per feature
- Update version to `1.6.8`

Key Changes Summary:
1. CSS Styling: Complete overhaul of `Select2` appearance to match Bootstrap `form-select` with your custom theme
2. JavaScript Feature: New generic input binding system using HTML data attributes for dynamic UI updates
3. Version Bump: Incremented from `1.6.7` to `1.6.8`

Author: bkader