feature: seed reset scheduler contract spec endpoint

[oreoluwa648]

Implement testnet seed reset scheduler and contract spec/ABI exposure endpoint

Overview

This PR adds automated seed reset scheduling for shared testnet environments and exposes active Soroban contract specifications through a registry-backed endpoint.

Changes

Testnet Seed Reset Scheduler (#556)

• Add scheduler for clearing and reseeding demo data on configurable intervals
• Support per-scope exclusions for environments that should persist longer
• Emit reports on reset outcomes and failures
• Add tests for schedule execution and exclusion rules

Contract Spec / ABI Exposure Endpoint (#555)

• Expose active Soroban contract spec/ABI through backend API
• Include contract version, WASM hash, and supported methods
• Cache responses and invalidate on registry changes
• Add tests for missing spec, stale spec, and multi-contract responses

Files Added

• Seed reset scheduler service
• Contract spec registry and endpoint
• Cache invalidation logic

Files Modified

• Demo data seeding service
• Contract registry integration

Closes #556
Closes #555