refactor: move non-reused widgets

lib/screens/libraries/content_state_builder.dart

@@ -0,0 +1,66 @@
+import 'package:flutter/material.dart';
+import '../../i18n/strings.g.dart';
+import 'empty_state_widget.dart';
+import 'error_state_widget.dart';
+
+/// A widget that handles loading, error, empty, and content states
+/// Provides a consistent UI pattern across the app for data-driven screens
+class ContentStateBuilder<T> extends StatelessWidget {
+  /// Whether data is currently loading
+  final bool isLoading;
+
+  /// Error message to display (null if no error)
+  final String? errorMessage;
+
+  /// The list of items to display
+  final List<T> items;
+
+  /// Icon to display when the list is empty
+  final IconData emptyIcon;
+
+  /// Message to display when the list is empty
+  final String emptyMessage;
+
+  /// Callback when user taps retry button
+  final VoidCallback onRetry;
+
+  /// Builder for the content when items are available
+  final Widget Function(List<T> items) builder;
+
+  const ContentStateBuilder({
+    super.key,
+    required this.isLoading,
+    required this.errorMessage,
+    required this.items,
+    required this.emptyIcon,
+    required this.emptyMessage,
+    required this.onRetry,
+    required this.builder,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    // Loading state (only show loading indicator if items list is empty)
+    if (isLoading && items.isEmpty) {
+      return const Center(child: CircularProgressIndicator());
+    }
+
+    // Error state (only show error if items list is empty)
+    if (errorMessage != null && items.isEmpty) {
+      return ErrorStateWidget(
+        message: errorMessage!,
+        icon: Icons.error_outline,
+        onRetry: onRetry,
+        retryLabel: t.common.retry,
+      );
+    }
+
+    // Empty state
+    if (items.isEmpty) {
+      return EmptyStateWidget(message: emptyMessage, icon: emptyIcon);
+    }
+
+    // Content state - delegate to builder
+    return builder(items);
+  }
+}