Add Fastmail email and calendar, multi-account neomutt

- mbsync: add Fastmail IMAP channel (rbw for credentials)
- msmtp: add Fastmail SMTP account
- neomutt: add fastmail account file, F2/F3 account switching macros
- vdirsyncer + khal: Fastmail CalDAV calendar sync
- zshrc: restore calsync alias

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

laptop/.config/vdirsyncer/config

@@ -0,0 +1,18 @@
+[general]
+status_path = "~/.local/share/vdirsyncer/status/"
+
+[pair fastmail_calendar]
+a = "fastmail_calendar_local"
+b = "fastmail_calendar_remote"
+collections = ["from a", "from b"]
+
+[storage fastmail_calendar_local]
+type = "filesystem"
+path = "~/.local/share/calendars/fastmail/"
+fileext = ".ics"
+
+[storage fastmail_calendar_remote]
+type = "caldav"
+url = "https://caldav.fastmail.com/dav/"
+username = "rob@rharbaugh.com"
+password.fetch = ["command", "rbw", "get", "fastmail-app-password"]