error-handling-patterns

Error handling patterns including exceptions, Result pattern, validation strategies, retry logic, and circuit breakers. **ALWAYS use when implementing error handling in backend code, APIs, use cases, or validation logic.** Use proactively for robust error handling, recovery mechanisms, and failure scenarios. Examples - "handle errors", "Result pattern", "throw exception", "validate input", "error recovery", "retry logic", "circuit breaker", "exception hierarchy".