Feat: add vault module

vault/src/session.rs

@@ -0,0 +1,22 @@
+//! Session manager for the vault crate (optional)
+
+use crate::data::KeyspaceData;
+use std::collections::HashMap;
+
+pub struct SessionManager {
+    unlocked_keyspaces: HashMap<String, KeyspaceData>,
+    current_keyspace: Option<String>,
+    current_keypair: Option<String>,
+    // ...
+}
+
+impl SessionManager {
+    pub fn new() -> Self {
+        Self {
+            unlocked_keyspaces: HashMap::new(),
+            current_keyspace: None,
+            current_keypair: None,
+        }
+    }
+    // ... methods for unlock, lock, select, timeout, etc.
+}