Decouple core Yaak logic from Tauri (#354)

crates/yaak-core/src/error.rs

@@ -0,0 +1,15 @@
+use thiserror::Error;
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error("Missing required context: {0}")]
+    MissingContext(String),
+
+    #[error("Configuration error: {0}")]
+    Config(String),
+
+    #[error("IO error: {0}")]
+    Io(#[from] std::io::Error),
+}