Add connection pooling with circuit breaker to OPC UA writer

- Add OPCUAConnectionManager singleton for connection pooling
- Implement circuit breaker pattern to fail fast when servers are unreachable
  - After connection failure, skip attempts for 30s (no blocking, no memory retention)
- Default to max_retries=1, retry_backoff=0 (fail fast, don't block pipeline)
- Use asyncua exception types (CONNECTION_ERROR_TYPES) instead of string matching
- Add support for all OPC UA numeric types

Author: alexnorell