test(core): add unit tests for untested core modules
Adds 113 tests covering:
- abc: RegistryABC (concrete implementation + edge cases)
- environment: Environment get/set, EnvironmentEnum
- pipes: BoolPipe, IPAddressPipe (incl. roundtrip + error cases)
- time: Cron (next(), intervals, invalid expression)
- utils: Cache (TTL, expiry, cleanup), get_value (incl. bug
documentation: cast result not returned for string->typed values),
JSONProcessor (nested objects, enums, defaults)
- property: classproperty (class access, instance access, subclass)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>