refactor(workspace): enforce layered crate boundaries

crates/aether-data/contracts/src/error.rs

@@ -0,0 +1,37 @@
+#[derive(Debug, thiserror::Error)]
+pub enum DataLayerError {
+    #[error("invalid configuration: {0}")]
+    InvalidConfiguration(String),
+
+    #[error("invalid input: {0}")]
+    InvalidInput(String),
+
+    #[error("postgres error: {0}")]
+    Postgres(String),
+
+    #[error("redis error: {0}")]
+    Redis(String),
+
+    #[error("sql error: {0}")]
+    Sql(String),
+
+    #[error("operation timed out: {0}")]
+    TimedOut(String),
+
+    #[error("unexpected database value: {0}")]
+    UnexpectedValue(String),
+}
+
+impl DataLayerError {
+    pub fn postgres(error: impl std::fmt::Display) -> Self {
+        Self::Postgres(error.to_string())
+    }
+
+    pub fn redis(error: impl std::fmt::Display) -> Self {
+        Self::Redis(error.to_string())
+    }
+
+    pub fn sql(error: impl std::fmt::Display) -> Self {
+        Self::Sql(error.to_string())
+    }
+}