Hand raise lead modal placeholder

What does this MR do and why?

Hand raise lead modal behind a feature flag

• Related to #334211 (closed)
• Part of the Vue component !70044 (merged)

Inspired by !66049 (merged)

How to set up and validate locally

Enable the flag to see

Feature.enable(:in_app_hand_raise_pql)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.