fix(ocpp): warn on OCPP 1.6 keys in template only, silent remap for internal code

fix(ocpp): warn on OCPP 1.6 keys in template only, silent remap for internal code

Simplify OCPP2_PARAMETER_KEY_MAP to a plain Map<string, string> and
make resolveKey always silent. Move warning to a one-shot template
validation pass (warnOnOCPP16TemplateKeys) called after template
loading, before init defaults. Warnings now only fire when the
operator uses OCPP 1.6 key names in an OCPP 2.0 station template,
not when internal cross-version code resolves keys.