fix: replace incorrect zero fallbacks for maximumPower and maximumAmperage

fix: replace incorrect zero fallbacks for maximumPower and maximumAmperage

Station physical properties (maximumPower, maximumAmperage) are validated
> 0 at startup. Using ?? 0 as fallback silently produces invalid states:
0W power limits blocking all charging, 0A amperage in config keys.

Replace with proper null guards that log errors and fail-open:
- getConnectorMaximumAvailablePower: return Infinity (no limit known)
- getMaximumAmperage: return undefined (caller already handles it)
- initializeOcppConfiguration: skip config key, log error
- getChargingStationChargingProfilesLimit: return limit uncapped
- getConnectorChargingProfilesLimit: return limit uncapped