fix: auto gen warning on example env and use correct cli flag in md gen

gen/gen_env.go

@@ -106,6 +106,8 @@ func buildEnvChildPath(parent string, child string) string {
 
 func compileEnv(entries []EnvEntry) []byte {
 	buffer := bytes.Buffer{}
+
+	buffer.WriteString("# This file is automatically generated by gen/gen_env.go. Do not edit manually.\n\n")
 	buffer.WriteString("# Tinyauth example configuration\n\n")
 
 	previousSection := ""