[WhatsApp] Archived chats should be treated as muted

[asemarafa]

Description

I noticed that for WhatsApp, archived chats are currently both visible and unmuted in nchat. This results in
receiving desktop/sound notifications for chats that are intended to be quiet (archived).

I compared this with the project's current Telegram implementation and found that Telegram simply hides archived chat
(by filtering for chatListMain). While the Telegram implementation might need its own bug report later (as it makes cha
inaccessible within nchat), for WhatsApp, the correct and expected behavior is that archived chats are implicitly
muted.

Observed Behavior

• Archived chats are visible in the chat list.
• They are not marked as muted in the UI.
• Notifications are still triggered when a new message is received in an archived chat.

Expected Behavior

• Archived chats should be automatically marked as muted.
• Unarchiving a chat should restore its previous manual mute state (e.g., if a user-set 8-hour mute was active before
  archiving, it should remain active after unarchiving).
• New messages in archived chats should not trigger notifications.

Steps to Reproduce

1. Archive a whatsapp contact or group on your phone.
2. Receive a message in that archived chat.
3. Observe that nchat triggers a notification and the chat appears unmuted.

Additional Context

I have a PR ready that utilizes the archive information already provided by the whatsmeow library (which is current
ignored by the project).

My implementation chooses to mute rather than hide archived chats. This ensures they remain accessible within
nchat (since there is no dedicated "Archive View") while strictly adhering to the "archived chats don't notify" rule.