Meta Ads: Add ad-level start/end schedule fields#2039

Please expose ad_schedule_start_time and ad_schedule_end_time from the Meta Marketing API Ad object as read fields in the Facebook Ads connector, including API and MCP/ChatGPT access.

These are ad-level scheduled start/end datetimes, not ad set start_time/end_time, ad creation timestamps, or reporting date_start/date_stop. The fields are defined in Meta’s official Business SDK:
https://github.com/facebook/facebook-python-business-sdk/blob/main/facebook_business/adobjects/ad.py

Use case: verify individual ads’ scheduled launch and end dates against an approved media plan. Ad set dates cannot substitute when different ads in one ad set have different schedules.

Please preserve timezone information and distinguish unset/unavailable values. Please also clarify supported ad types/API versions and any current workaround.