Remove mock protocol APY sources; implement real protocol rate fetchers

[robertocarlous]

Problem

Protocol scanning uses mocked APY/TVL values (src/agent/scanner.ts). This makes the agent's decisions unreliable and invalidates production claims.

Acceptance criteria

• Replace mock fetchers with real data sources for each supported protocol (Blend, Stellar DEX pools, Luma)
• Add timeouts, retries, and circuit breaker behavior per upstream
• Persist raw source data + computed APY in ProtocolRate for auditability
• Add integration tests that stub upstream HTTP responses
• Add metrics: fetch duration, failures per source, stale-rate detection

Priority

P0 / Critical

[anoncon]

Hello,

I’m a developer with 4 years of hands-on experience working on production-grade systems and contributing to collaborative, open-source environments. I’ve carefully read through this issue and fully understand the problem it addresses, the expected outcomes, and the constraints outlined in the acceptance criteria.