feat(frontend): Add Interactive Sandbox/Demo Mode Using Mocked Data for Prospective Users

[Dydex]

Rationale & Scope

Let prospective users explore the full dashboard experience with realistic mocked data before connecting a real wallet or submitting KYC information.

Concrete Tasks

• Build a "Try Demo" entry point serving a mocked data layer instead of live API/contract calls.
• Add a persistent banner indicating demo mode with a clear exit/upgrade-to-real-account path.
• Ensure no demo-mode actions can accidentally trigger real wallet or backend calls.

Acceptance Criteria

• Demo mode renders realistic dashboard data without any live wallet connection or backend writes.
• Users can exit demo mode at any point and land cleanly on the real onboarding flow.

Suggested Branch Name

git checkout -b feat/frontend-sandbox-demo-mode