Fix mobile spacing scale

[GuilhermeAlbert]

Summary

• restore 16dp page gutters and component padding across the mobile UI
• replace ambiguous spacing utilities affected by the literal design-token scale
• add a contract test preventing accidental reuse of the 4dp token as Tailwind 16dp spacing

Verification

• lint
• typecheck
• 67 suites / 252 tests
• Expo Doctor 20/20
• physical-device baseline captured on Motorola One Fusion