1. Add `lib/utils/validation.ts` form schemas

[DeFiVC]

What: Add Zod schemas for form validation (profile, course creation, quiz submission).

Why: Forms need schema-based validation. Zod provides type-safe validation with good error messages.

Scope: Add schemas for: profileUpdate, courseCreate, quizSubmit, rewardClaim. Export types from schemas.

Acceptance criteria:

• Schemas validate correctly
• Types are exported
• Error messages are clear
• Schemas are composable

Technical context: src/lib/utils/validation.ts — validation utils. src/app/(auth)/onboarding/page.tsx — onboarding form.

---