UX: message detail view needs obvious close and next/previous navigation

[the-luap]

Summary

When reading a message from a mailbox, there does not appear to be an obvious way to close the current message and return to the message list, or to move directly to the next/previous message.

This makes high-volume mailbox triage very slow, because each message has to be handled through navigation that is not immediately discoverable.

Current behavior

1. Open a mailbox/inbox.
2. Click an email/message.
3. The message opens.
4. There is no obvious visible control to:
   • close the message and return to the list,
   • go to the next message,
   • go to the previous message.

If such controls exist, they are not discoverable enough in the current UI.

Expected behavior

The message detail view should provide clear, always-visible navigation controls, for example:

• a back/close button to return to the current mailbox list,
• next / previous message buttons,
• keyboard shortcuts such as:
  • Esc = close message / return to list,
  • j / k or arrow keys = next / previous message,
• optional disabled states at the beginning/end of the list.

Why this matters

This is a core workflow for email clients. Users managing many emails need fast triage without returning to the mouse-heavy mailbox list after every single message.

Without close/next/previous controls, reviewing a mailbox becomes inefficient and unintuitive.

Environment

• Kurrier version/image: v1.1.13
• Runtime: production Docker deployment

[the-luap]

I have this implemented locally already.

Relevant local commits:

4e0124a fix: harden mailbox routes and thread navigation
c905aae fix: improve mail thread navigation and folder state

The local implementation adds visible thread navigation controls and improves folder-state handling so the user can return to the list / move between messages more reliably.

This was built and deployed successfully in a production Docker/Swarm setup. I can open a PR with the tested local fix if maintainers want it.

[krokhale]

Can you attach an image of the changes? Open a PR.