Campaign creation wizard with validation and preview

[joelpeace48-cell]

Epic: Frontend Features

Summary

Multi-step wizard for operators to create campaigns (metadata, rewards config, multipliers) with live preview.

Background & Problem

Campaign setup is core operator UX; a guided wizard reduces misconfiguration and support load.

Acceptance Criteria

• Wizard validates each step and previews the result.
• Submits config on-chain + off-chain atomically.
• Covered by E2E test.

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Filed as part of the mainnet-readiness & world-class roadmap. Scope is intentionally small enough for one focused PR; comment to claim.