Harden external API clients with timeouts and retries

[robertocarlous]

Body:

Calls to Twilio, Stellar, and Anthropic lack consistent timeouts and retry behavior. Wrap these clients with a shared HTTP client or adapter that implements timeouts, exponential backoff, and a circuit breaker for repeated failures.

Acceptance Criteria:

• External client wrappers implement timeouts and retry logic.
• Circuit breaker prevents calls after a configurable failure threshold.
• Integration tests simulate failures to confirm fallback behavior.

[sammajayi]

Hi maintainer, I can get this done in less than 24 hours.

[grantfox-oss]

🦊 GrantFox — @sammajayi has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #147)
2. Your PR will be reviewed by the Neurowealth maintainers

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