refactor: code-quality cleanup — utils usage, logic consolidation, export hygiene...

refactor: code-quality cleanup — utils usage, logic consolidation, export hygiene (#2036)

* refactor(ui-server): use isEmpty for outstanding-hashid checks

* refactor(ui-server): extract releaseRequest for broadcast request release

* refactor(ocpp): lift requestHandler into base template method

* refactor(utils): add isOCPP20x helper and route version predicates

* refactor(charging-station): single-source the request-statistics gate

* refactor(utils): use isNotEmptyString/isNotEmptyArray predicates

* refactor: drop dead exports and redundant re-export

* refactor(auth): rename AuthorizationStatus enum to AuthResultStatus

* refactor(ocpp): drop now-redundant logRequestHandlerError module-name param

* docs(charging-station): document recordRequestStatistic public method

* refactor(ocpp): route VariableMetadata mutability/persistence checks through predicates

* refactor(ocpp): unexport in-file-only parseJsonSchemaFile