feat(GODT-2759): CLI debug commands

Add debug commands to CLI to diagnose potential bride problems.
Currently we only have a command which validates whether the state of
all the mailboxes reported by IMAP matches what is currently available
on the proton servers.

internal/frontend/cli/frontend.go

@@ -312,6 +312,19 @@ func New(
 	})
 	fe.AddCmd(telemetryCmd)
 
+	dbgCmd := &ishell.Cmd{
+		Name: "debug",
+		Help: "Debug diagnostics ",
+	}
+
+	dbgCmd.AddCmd(&ishell.Cmd{
+		Name: "mailbox-state",
+		Help: "Verify local mailbox state against proton server state",
+		Func: fe.debugMailboxState,
+	})
+
+	fe.AddCmd(dbgCmd)
+
 	go fe.watchEvents(eventCh)
 
 	go func() {