Add email support with notmuch, mbsync, and msmtp

Set up complete email workflow in Emacs using:
- notmuch for email indexing and UI
- mbsync for IMAP synchronization from proton.johnogle.info
- msmtp for SMTP sending via port 25 with PLAIN auth
- systemd timer for automatic sync every 5 minutes

Configuration includes:
- New email role at home/roles/email with all mail tools
- Doom Emacs notmuch module enabled with saved searches
- Secure credential retrieval via rbw from Bitwarden
- Fixed systemd service PATH to access rbw-agent
- TLS/STARTTLS for secure connections

Email role enabled on nix-book (laptop-compact profile).

home/roles/emacs/doom/init.el

@@ -177,7 +177,7 @@
 
        :email
        ;;(mu4e +org +gmail)
-       ;;notmuch
+       notmuch
        ;;(wanderlust +gmail)
 
        :app