Created project base structure, state management, router and login

lib/providers/api_client_provider.dart

@@ -0,0 +1,21 @@
+import 'package:my_linkding/providers/server_instances_provider.dart';
+import 'package:my_linkding/services/api_client.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+part 'api_client_provider.g.dart';
+
+@Riverpod(keepAlive: true)
+class ApiClientProvider extends _$ApiClientProvider {
+  @override
+  ApiClient? build() {
+    final savedInstances = ref.watch(serverInstancesProvider);
+    if (savedInstances.isNotEmpty) {
+      return ApiClient(serverInstance: savedInstances[0]);
+    }
+    return null;
+  }
+
+  void setApiClient(ApiClient client) {
+    state = client;
+  }
+}