feat(storage): 添加 StorageError 类型

src/storage/error.rs

@@ -0,0 +1,16 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum StorageError {
+    #[error("session not found: {0}")]
+    NotFound(String),
+
+    #[error("session already exists: {0}")]
+    AlreadyExists(String),
+
+    #[error("database error: {0}")]
+    Database(#[from] sqlx::Error),
+
+    #[error("serialization error: {0}")]
+    Serialization(String),
+}