Let Dex Copilot use connected iMessage and WhatsApp conversations

Allow Dex Copilot to use authorized conversation data from connected iMessage and WhatsApp sources when users search their network or look for people to follow up with.

Desired outcome:

• Let users choose which connected sources Copilot should use, including excluding LinkedIn.
• Use supported iMessage and WhatsApp conversation data for contact and follow-up searches.
• Explain source coverage, retention, and permission limits clearly.
• Distinguish an integration being connected from its data being available to Copilot.

Current gap: Messaging integrations can appear connected while Copilot says it cannot access their conversations.