chore(monorepo): relocate client files

apps/client/src/services/note_attribute_cache.ts

@@ -0,0 +1,24 @@
+import type FAttribute from "../entities/fattribute.js";
+
+/**
+ * The purpose of this class is to cache the list of attributes for notes.
+ *
+ * Cache invalidation granularity is global - whenever a write operation is detected to notes, branches or attributes,
+ * we invalidate the whole cache. That's OK, since the purpose for this is to speed up batch read-only operations, such
+ * as loading the tree which uses attributes heavily.
+ */
+class NoteAttributeCache {
+    attributes: Record<string, FAttribute[]>;
+
+    constructor() {
+        this.attributes = {};
+    }
+
+    invalidate() {
+        this.attributes = {};
+    }
+}
+
+const noteAttributeCache = new NoteAttributeCache();
+
+export default noteAttributeCache;