fix(ocpp16): fix StopTransaction unit schema and ChargingSchedule field name

fix(ocpp16): fix StopTransaction unit schema and ChargingSchedule field name

- Add missing 'Celsius' to StopTransaction.json unit enum (M-2/SP-1)
  The runtime schema had only 'Celcius' (legacy typo) while the OCA
  official schema has both. TS enum produces 'Celsius' which was
  rejected by AJV when ocppStrictCompliance was enabled.

- Rename minChargeRate to minChargingRate in OCPP16ChargingSchedule (RST-01)
  Field name typo caused JSON serialization mismatch with spec §7.13
  and schema 'minChargingRate', breaking SetChargingProfile and
  GetCompositeSchedule payloads.