operating-hours property definition misses timezones and is different in api.md and ExistingFormatReview in the wiki

The wiki deviates from the definition found in api.md.
In the wiki operating-hours is defined as as a dict of dicts (day -> {from, to}) and api.md says it is an string type. At the moment the api,first.org is using untyped string type. For better support in tools to show availability it would be good if operating hours are saved in a structured way.

Also including timezone information to these operating hours to be useful.

Compare the operating-hours definitions in api.md and the ExistingFormatReview entry in the wiki, then inspect how the api.first.org API currently represents the field. Define a consistent structured representation that includes timezone information and update the documented definition and API behavior so both sources agree.

Written by the indexing model from the issue text.