Add circuit breaker for external services

[meshackyaro]

Description

External service outages (Pinata) cause cascading failures. Need circuit breaker to fail fast.

Component

Backend

Difficulty

🔴 Hard

Tasks

• Implement circuit breaker with opossum
• Configure failure thresholds
• Add half-open state for recovery
• Apply to IPFS/external services
• Test with simulated outages

Acceptance Criteria

• Circuit breaker prevents cascades
• Service recovery detected
• Circuit state observable

Estimated Time

3-4 days