Feat/fe create quest wizard

[Ezeh20]

Summary

closes #260

• Add the 6-step Create a Quest wizard (Basics → Eligibility → Tasks → Rewards → Schedule → Review & publish), rendered as a full-viewport drawer.
• Stepper shows progress/validation state per step; Continue is gated by per-step client validation (title/description required, at least one titled task, reward budget within available balance, valid schedule window).
• Rewards step computes reward-per-winner and a required/available/remaining balance summary live, including platform + network fee estimates.
• "Preview" opens a participant-facing preview modal of the quest; "Save as draft" and "Publish quest" are stubbed (no backend calls yet) — publish shows the success screen (Close / View quest) using the new star-q.svg asset.

Test plan

• tsc --noEmit passes
• eslint passes on changed files
• Verified locally: full wizard flow Basics → Publish, back/forward step navigation, Preview modal, drawer overlay dims + covers sidebar/top nav, Save as draft redirect

[Kaylahray]

Excellent job @Ezeh20