Move power status value interpretation from hardcoded logic to OID set configuration.
Each UPS model now defines its own value mappings (e.g., CyberPower: 2=online, 3=onBattery).
Fixes incorrect status display where UPS showed "On Battery" when actually online.
Changes:
- Add POWER_STATUS_VALUES to IOidSet interface
- Define value mappings for all UPS models (cyberpower, apc, eaton, tripplite, liebert)
- Refactor determinePowerStatus() to use OID set mappings instead of hardcoded values
- CyberPower now correctly interprets value 2 as online (was incorrectly onBattery)
- Add Buffer import from node:buffer to manager.ts and types.ts
- Fix error handling type assertions (error/retryError/stdError as unknown)
- Add explicit type annotation to byte parameter in isPrintableAscii check
- All tests now passing (3 SNMP tests + 10 logger tests)
