Improve LibreSign sidebar

As suggested in https://github.com/LibreSign/libresign/issues/4160#issuecomment-2548723509

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Describe the solution you'd like
The sidebar should contain everything related to LibreSign and that document.

I'll refer to a group signature when 1 or more parties need to sign a specific document "at the same time" for that document to be marked as fully signed by all parties. 1 person needs to sign: group signature, 10 people need to sign the document: group signature.

• All the group signatures completed:
  • Who requested it and when
  • Who signed it, when and how
  • Open/download the signed document
  • Delete the signed document if allowed (admin setting?)
• All the group signatures not yet completed (all of the above +:)
  • Who needs to sign it
    • Actions:
      • Resend signature request
        • Possible: By email + If instance account (or federated account): Send request by chat with Talk
      • Remove signature request

EDIT:
I forgot the main action: Ask for signature 😂

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

No files or tests are named. Start with issue 4160 and its linked suggestion, then define the sidebar flows for requesting signatures and managing completed and pending group signatures; done means the requested actions and signer details are covered.