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/config.el

@@ -159,6 +159,32 @@
   (dolist (module '("bbdb" "buffer" "elisp" "emacs" "gnus" "os" "search-and-replace" "url"))
     (gptel-tool-library-load-module module)))
 
+;; Notmuch email configuration
+(after! notmuch
+  (setq notmuch-search-oldest-first nil
+        notmuch-show-logo nil
+        notmuch-fcc-dirs "proton/Sent"
+
+        ;; User identity
+        user-mail-address "john@ogle.fyi"
+        user-full-name "John Ogle"
+
+        ;; Sending mail via msmtp
+        message-send-mail-function 'message-send-mail-with-sendmail
+        sendmail-program (executable-find "msmtp")
+        message-sendmail-envelope-from 'header
+        mail-envelope-from 'header
+        mail-specify-envelope-from t
+
+        ;; Saved searches for quick access
+        notmuch-saved-searches
+        '((:name "inbox"   :query "tag:inbox"                    :key "i")
+          (:name "unread"  :query "tag:unread"                   :key "u")
+          (:name "flagged" :query "tag:flagged"                  :key "f")
+          (:name "sent"    :query "tag:sent"                     :key "t")
+          (:name "drafts"  :query "tag:draft"                    :key "d")
+          (:name "all"     :query "*"                            :key "a"))))
+
 ;; Whenever you reconfigure a package, make sure to wrap your config in an
 ;; `after!' block, otherwise Doom's defaults may override your settings. E.g.
 ;;