domain: add Organization entities and ports (Album, Tag, Collection, FilterCriteria)

crates/domain/tests/entities/album.rs

@@ -0,0 +1,27 @@
+use domain::entities::Album;
+use domain::errors::DomainError;
+use domain::value_objects::SystemId;
+
+#[test]
+fn add_and_remove_asset() {
+    let mut album = Album::new("Vacation", SystemId::new());
+    let asset = SystemId::new();
+    let user = SystemId::new();
+
+    album.add_asset(asset.clone(), user.clone()).unwrap();
+    assert_eq!(album.asset_count(), 1);
+
+    album.remove_asset(&asset).unwrap();
+    assert_eq!(album.asset_count(), 0);
+}
+
+#[test]
+fn cannot_add_duplicate() {
+    let mut album = Album::new("Vacation", SystemId::new());
+    let asset = SystemId::new();
+    let user = SystemId::new();
+
+    album.add_asset(asset.clone(), user.clone()).unwrap();
+    let result = album.add_asset(asset, user);
+    assert!(matches!(result, Err(DomainError::Conflict(_))));
+}