Epic: Spacing Update

[francisrupert]

Audit and update all sizing and spacing properties across all base styles and components to tighten spacing and alignment to a stricter 4px rhythm and baseline grid.

• [x] #496
• [x] #526
• [x] #495
• [x] #524
• [x] #525
• [x] #515
• [x] #521
• [x] #518
• [x] #520
• [x] #515
• [x] #529
• [x] #523