Improve UX of manual completion step

[I-Dont-Remember]

• ❔ change from being aimed at individual user, to being available to team through App Home, just like the managing of scheduled messages.
  • Store and let any team member view the currently waiting 'Manual completion' step executions.
• ✅ Let user add notes that will appear as context alongside the execution id - if it's a couple days later, you won't remember which message was for which execution.
• Have a button on the message sent with execution ID (that will now include notes as well) that opens the Finish manual execution modal from the App Home, but with the ID value already prefilled for them.
  • Seems like it makes sense to hide the execution ID from users as much as possible, progressive disclosure & etc.

[I-Dont-Remember]

First stab in #47 with changing the message to have 2 buttons + some context info. Will leave it at that for now until I get real user feedback suggesting changes vs just going with whatever pops in my head.

Might be useful to have a Why did you choose to Continue/Stop this optional field, which would then have us switch from two buttons to a single one that pops a modal. That might just be extra noise though, we will see.