fix(lint): add nosec for mail delegate exec.Command

gosec G204 warning - the cmdName comes from user configuration
(mail_delegate setting), not untrusted input.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/mail.go

@@ -68,6 +68,7 @@ Examples:
 		cmdArgs := append(parts[1:], args...)
 
 		// Execute the delegate command
+		// #nosec G204 - cmdName comes from user configuration (mail_delegate setting)
 		execCmd := exec.Command(cmdName, cmdArgs...)
 		execCmd.Stdin = os.Stdin
 		execCmd.Stdout = os.Stdout