refactor(workspace): enforce layered crate boundaries

crates/aether-data/contracts/src/repository/candidate_selection/mod.rs

@@ -0,0 +1,8 @@
+mod types;
+
+pub use types::{
+    MinimalCandidateSelectionReadRepository, MinimalCandidateSelectionRepository,
+    StoredMinimalCandidateSelectionRow, StoredPoolKeyCandidateOrder,
+    StoredPoolKeyCandidateRowsByKeyIdsQuery, StoredPoolKeyCandidateRowsQuery,
+    StoredProviderModelMapping, StoredRequestedModelCandidateRowsQuery,
+};