refactor: restructure domain crate by bounded context

crates/domain/tests/organization/entities.rs

@@ -0,0 +1,42 @@
+use domain::entities::{Album, AssetTag, Tag, TagSource};
+use domain::errors::DomainError;
+use domain::value_objects::SystemId;
+
+// --- Album ---
+
+#[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(_))));
+}
+
+// --- Tag ---
+
+#[test]
+fn manual_tag_has_full_confidence() {
+    let tag = Tag::new_manual("sunset");
+    assert_eq!(tag.name, "sunset");
+    assert_eq!(tag.tag_source, TagSource::UserManual);
+
+    let asset_tag = AssetTag::new_manual(SystemId::new(), tag.tag_id.clone(), SystemId::new());
+    assert_eq!(asset_tag.confidence, 1.0);
+    assert!(asset_tag.tagged_by_user_id.is_some());
+}

crates/domain/tests/organization/mod.rs

@@ -0,0 +1 @@
+mod entities;