feat: Add initial backend server with user authentication, session management, and playlist CRUD functionality.

bin/pubspec.yaml

@@ -9,5 +9,9 @@ environment:
 dependencies:
   shelf: ^1.4.1
   shelf_static: ^1.1.2
+  shelf_router: ^1.1.4
   http: ^1.2.0
   args: ^2.4.2
+  sqlite3: ^2.4.0
+  crypto: ^3.0.3
+  uuid: ^4.3.3