Use backend access checks for gated content

[Lakes41]

Summary

Refactor gated content decisions so they can use the backend access policy engine instead of relying only on client-side tier and role checks.

Current Behaviour

components/gated.tsx locally compares roles, membership tier, and membership active status. This duplicates policy logic in the frontend and may diverge from guildpass-core.

Expected Behaviour

The frontend should ask the access API whether the connected wallet can access a resource, then render allowed, denied, loading, or error states from that decision.

Suggested Implementation

Extend AccessApi with a checkAccess(resourceId, address) method. Implement it in mock and live clients. Update gated pages to pass a resource identifier instead of hard-coded tier logic where practical.

Files or Areas Likely Affected

• components/gated.tsx
• app/resources/alpha/page.tsx
• app/events/demo/page.tsx
• lib/api/types.ts
• lib/api/live.ts
• lib/api/mock.ts

Acceptance Criteria

• AccessApi exposes a typed access check method
• LiveAccessApi calls the backend access check endpoint
• MockAccessApi simulates allow and deny decisions consistently
• Gated pages render based on backend-style access decisions
• Denied states include a safe reason message
• Existing tier and role props are either mapped or deprecated cleanly

Additional Notes

Assumption: guildpass-core exposes or will expose a resource access decision endpoint. If not, document the expected contract before implementing the live client.

[web3nova]

I've reviewed the issue description, and I'm confident I can implement all the requested details smoothly.​Please assign this issue to me! I can have a PR ready for review in a few hours. Thanks