feat(web): add widget config dialog and layout management controls

Add per-widget configuration dialog (WidgetConfigDialog) with settings
infrastructure ready for future configSchema-based forms. Add layout
management controls: reset to default, edit/done toggle, and widget
gear icon for configuration. Wire onEditWidget through WidgetGrid to
BaseWidget.

Implements TW-WDG-004 and TW-WDG-005.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/components/widgets/WidgetGrid.tsx

@@ -22,6 +22,7 @@ export interface WidgetGridProps {
   layout: WidgetPlacement[];
   onLayoutChange: (layout: WidgetPlacement[]) => void;
   onRemoveWidget?: (widgetId: string) => void;
+  onEditWidget?: (widgetId: string) => void;
   isEditing?: boolean;
   className?: string;
 }
@@ -30,6 +31,7 @@ export function WidgetGrid({
   layout,
   onLayoutChange,
   onRemoveWidget,
+  onEditWidget,
   isEditing = false,
   className,
 }: WidgetGridProps): React.JSX.Element {
@@ -183,6 +185,12 @@ export function WidgetGrid({
                 id={item.i}
                 title={widgetDef.displayName}
                 description={widgetDef.description}
+                {...(isEditing &&
+                  onEditWidget && {
+                    onEdit: (): void => {
+                      onEditWidget(item.i);
+                    },
+                  })}
                 {...(isEditing &&
                   onRemoveWidget && {
                     onRemove: (): void => {