feat: add Control Room with containers and stacks management

- Add Control Room page with stacks sidebar and containers list
- Implement container actions (start/stop/restart) with snackbars
- Add container logs viewer dialog
- Add search/filter for both stacks and containers lists
- Add external links for Portainer and Netdata (url_launcher)
- Add VS Code launch configuration for Flutter web debugging

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/shared/components/data_grid/data_grid_state.dart

@@ -0,0 +1,62 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'data_grid_state.freezed.dart';
+
+/// State for a DataGrid instance.
+@freezed
+class DataGridState<T> with _$DataGridState<T> {
+  const factory DataGridState({
+    /// Current items being displayed.
+    @Default([]) List<T> items,
+
+    /// Total count of items (may differ from items.length for pagination).
+    @Default(0) int totalCount,
+
+    /// Whether data is currently loading.
+    @Default(false) bool isLoading,
+
+    /// Whether initial load is in progress.
+    @Default(true) bool isInitialLoad,
+
+    /// Error that occurred during loading.
+    Object? error,
+
+    /// Current search query.
+    @Default('') String searchQuery,
+
+    /// Index of the column currently sorted by.
+    int? sortColumnIndex,
+
+    /// Whether sort is descending.
+    @Default(false) bool sortDescending,
+
+    /// Currently selected item IDs (if selectable).
+    @Default({}) Set<Object> selectedIds,
+
+    /// Current page (for paginated mode).
+    @Default(0) int currentPage,
+
+    /// Whether more items can be loaded (for infinite scroll).
+    @Default(false) bool hasMore,
+  }) = _DataGridState<T>;
+}
+
+/// Extension methods for DataGridState.
+extension DataGridStateX<T> on DataGridState<T> {
+  /// Whether the grid has an error.
+  bool get hasError => error != null;
+
+  /// Whether the grid is empty (no items and not loading).
+  bool get isEmpty => items.isEmpty && !isLoading && !hasError;
+
+  /// Whether all visible items are selected.
+  bool get allSelected =>
+      items.isNotEmpty && selectedIds.length == items.length;
+
+  /// Whether some (but not all) items are selected.
+  bool get someSelected =>
+      selectedIds.isNotEmpty && selectedIds.length < items.length;
+
+  /// Number of selected items.
+  int get selectedCount => selectedIds.length;
+}