Add validated identifiers, Hash32, Timestamp and DataClass to proto

Implemented-By: Laguna S 2.1 (OpenCode)

crates/proto/src/class.rs

@@ -0,0 +1,9 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum DataClass {
+    Public,
+    Private,
+    Secret,
+}