Add getAllFromIndex method for efficient sorted queries

- Add getAllFromIndex to StorageBackend interface for index-based queries
- Implement getAllFromIndex in IndexedDBStorageBackend using cursor API
- Update SessionsStore.getAllMetadata to use lastModified index
- Enables database-native sorting instead of fetching all keys and sorting in JS

Benefits:
- Much faster for large datasets (uses IndexedDB cursor with direction)
- Reduces memory usage (no need to load all keys first)
- Leverages existing indices for optimal performance

packages/web-ui/src/storage/backends/indexeddb-storage-backend.ts

@@ -96,6 +96,34 @@ export class IndexedDBStorageBackend implements StorageBackend {
 		}
 	}
 
+	async getAllFromIndex<T = unknown>(
+		storeName: string,
+		indexName: string,
+		direction: "asc" | "desc" = "asc",
+	): Promise<T[]> {
+		const db = await this.getDB();
+		const tx = db.transaction(storeName, "readonly");
+		const store = tx.objectStore(storeName);
+		const index = store.index(indexName);
+
+		return new Promise((resolve, reject) => {
+			const results: T[] = [];
+			const request = index.openCursor(null, direction === "desc" ? "prev" : "next");
+
+			request.onsuccess = () => {
+				const cursor = request.result;
+				if (cursor) {
+					results.push(cursor.value as T);
+					cursor.continue();
+				} else {
+					resolve(results);
+				}
+			};
+
+			request.onerror = () => reject(request.error);
+		});
+	}
+
 	async clear(storeName: string): Promise<void> {
 		const db = await this.getDB();
 		const tx = db.transaction(storeName, "readwrite");

packages/web-ui/src/storage/stores/sessions-store.ts

@@ -42,11 +42,8 @@ export class SessionsStore extends Store {
 	}
 
 	async getAllMetadata(): Promise<SessionMetadata[]> {
-		const keys = await this.getBackend().keys("sessions-metadata");
-		const metadata = await Promise.all(
-			keys.map((key) => this.getBackend().get<SessionMetadata>("sessions-metadata", key)),
-		);
-		return metadata.filter((m): m is SessionMetadata => m !== null);
+		// Use the lastModified index to get sessions sorted by most recent first
+		return this.getBackend().getAllFromIndex<SessionMetadata>("sessions-metadata", "lastModified", "desc");
 	}
 
 	async delete(id: string): Promise<void> {

packages/web-ui/src/storage/types.ts

@@ -48,6 +48,14 @@ export interface StorageBackend {
 	 */
 	keys(storeName: string, prefix?: string): Promise<string[]>;
 
+	/**
+	 * Get all values from a specific store, ordered by an index.
+	 * @param storeName - The store to query
+	 * @param indexName - The index to use for ordering
+	 * @param direction - Sort direction ("asc" or "desc")
+	 */
+	getAllFromIndex<T = unknown>(storeName: string, indexName: string, direction?: "asc" | "desc"): Promise<T[]>;
+
 	/**
 	 * Clear all data from a specific store.
 	 */