feat(frontend): implement admin testnet health console (#581)

[HushLuxe]

Summary

Resolves #581 (FE-46: Admin Testnet Health Console).

This PR introduces a dedicated Admin Testnet Health Console in the frontend dashboard. It aggregates contract registry status, indexer lag metrics, deep readiness smoke probes, and environment parity metadata from the backend /admin/rc-validation/report endpoint.

Key Changes

1. New Frontend Component (TestnetHealthConsole.tsx):

   • KPI Cards & Readiness Banner: Displays overall release readiness state (READY, DEGRADED, BLOCKED), release gate status, network, environment, and last refreshed timestamp with manual refresh controls.
   • Contract Registry Status Panel: Shows active vs expected contracts, authoritative state, version, and link to registry webhooks (/webhooks).
   • Indexer Lag Metrics Panel: Tracks current network ledger vs last indexed ledger, lag ledgers, enforcement mode (Blocking vs Monitoring), and link to transaction history (/dashboard).
   • Smoke Test Probes Panel: Displays deep subsystem health readiness checks (Supabase, Horizon RPC, Soroban RPC, Job Queue, Ingestion, Migrations).
   • Environment Parity & Metadata Panel: Shows parity check results and deployment metadata.
   • Blockers & Remediation Log: Actionable table displaying blockers with severity badges (Critical, Warning, Info), category filters (Smoke, Registry, Lag, Environment), search filter, remediation guidance, and direct action links.

2. Admin Dashboard Integration (app/frontend/src/app/admin/page.tsx):

   • Added tabbed navigation allowing admins to toggle between Testnet Health Console, Safety Controls, and Audit Logs.

3. Backend Spec Refactor (contract-registry.service.unit.spec.ts):

   • Removed obsolete DeploymentValidationService references in unit tests so that the backend contract registry test suite passes 100% (9/9 tests passed).

Verification & Testing

• Tested backend unit tests: pnpm --filter @quickex/backend exec jest src/contracts/contract-registry.service.unit.spec.ts (Passed).
• Verified TypeScript compilation: pnpm --filter frontend exec tsc --noEmit (0 errors).
• Built fallback operational data handler to ensure console stability when backend endpoints are initializing or restarting.

Closes #581

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[Cedarich]

Kindly fix workflow