refactor(button): improve MD3 compliance and modernize content API #4928

Refactor Button to improve Material Design 3 compliance, remove problematic children patterns, improve performance characteristics, and modernize the public API.

Problems

• Current API relies heavily on children composition in ways that are difficult to optimize
• Internal layout logic is tightly coupled to arbitrary child structures
• MD3 behaviors and visuals are not fully aligned with current Material guidelines
• Rendering performance can degrade in large lists or frequently updated screens
• Type safety and discoverability of the API can be improved
• The component has inconsistent behavior between platforms and edge cases

Focus Areas

• Remove implicit text child handling
• Improve icon + label composition
• Standardize loading and disabled states
• Improve ripple and state layer behavior
• Reduce nested render structure
• Improve accessibility semantics

Proposed API Direction

Instead of:

<Button icon="plus">Create</Button>

Prefer:

<Button label="Create" icon="plus" />

Performance Opportunities

• Memoize content container
• Avoid cloning children
• Reduce dynamic style allocations
• Optimize ripple rendering