fix(ocpp16): ocpp 1.6 conformance audit — 8 findings remediated

fix(ocpp16): ocpp 1.6 conformance audit — 8 findings remediated

Fixes validated against OCPP 1.6 Edition 2 spec and OCA JSON schemas:

- DT-01: DataTransfer returns UnknownMessageId when vendorId matches
  but messageId is provided (spec §4.3)
- CCP-01: ClearChargingProfile applies id/stackLevel/purpose filters
  when connectorId is specified instead of clearing all profiles (spec §5.5)
- TM-01/02/03: TriggerMessage handles DiagnosticsStatusNotification,
  FirmwareStatusNotification and MeterValues triggers (spec §5.17)
- GAP-03: ChangeConfiguration rejects non-integer and negative values
  for known integer config keys (spec §5.3)
- GAP-11: Reset distinguishes Hard/Soft — hard reset skips graceful
  transaction stopping (spec §5.14)
- GCS-02: GetCompositeSchedule implements connectorId=0 to report
  total grid consumption across all connectors (spec §5.7)