Fix: dialog scroll, isDirty false positive, mobile edit btn, widget copy

Five fixes:

1. Dialog mobile scroll: DialogContent now has max-h-[calc(100dvh-2rem)]
   overflow-y-auto so dialogs that don't fit on screen can scroll
   instead of clipping their footer (and Cancel button) off-screen.

2. isDirty false positive: WidgetConfigDialog's SheetForm used
   isDirty={draft !== null} which was true the moment you opened edit
   mode, even with no changes. Now stores a draftBaseline at startEdit
   time and compares JSON.stringify(draft) !== JSON.stringify(baseline).
   The discard-confirmation only appears when something actually changed.

3. Mobile edit button always visible: the widget card's edit button was
   opacity-0 group-hover:opacity-100 (hover-only). Changed to
   md:opacity-0 md:group-hover:opacity-100 — always visible below md,
   hover-reveal at md+.

4. Copy button for referenced widgets: WidgetInstanceCard gains an onCopy
   prop. On the Dashboard, referenced widgets get a Copy icon button that
   triggers detachRef (creates an independent clone). The edit button on
   referenced widgets edits the original (shared config).

5. ConfirmDialog Cancel: fixed by #1 (the Cancel button was off-screen
   on mobile dialogs that couldn't scroll).

128 tests pass; lint/build green.

frontend/src/pages/Dashboard.tsx

@@ -31,7 +31,7 @@ import {
 	useDeleteDashboardShortcut,
 	useSaveDashboardShortcut,
 } from "../hooks/useDashboard";
-import { useWidgetInstances, useWidgetReferences } from "../hooks/useWidgets";
+import { useDetachWidgetReference, useWidgetInstances, useWidgetReferences } from "../hooks/useWidgets";
 import { useServiceInstances } from "../hooks/useServices";
 import { useIsMobile } from "../hooks/useIsMobile";
 import type {
@@ -139,11 +139,15 @@ function MobileWidgetSections({
 							{SECTION_META[section.id].label}
 						</h3>
 						{section.widgets.map((widget) => (
-							<WidgetInstanceCard key={widget.id} widget={widget} onEdit={onEditWidget ? (id) => onEditWidget(id) : undefined} />
+							<WidgetInstanceCard
+								key={widget.id}
+								widget={widget}
+								onEdit={onEditWidget ? (id) => onEditWidget(id) : undefined}
+							/>
 						))}
 					</section>
 				))}
-				</div>
+			</div>
 		</>
 	);
 }
@@ -468,6 +472,13 @@ export function Dashboard() {
 			.sort((a, b) => a.sort_order - b.sort_order);
 	}, [widgetInstances, widgetReferences]);
 
+	// Track which visible widgets are references (for the copy/detach button).
+	const referencedWidgetIds = useMemo(
+		() => new Set(widgetReferences.map((r) => r.widget.id)),
+		[widgetReferences],
+	);
+	const detachRef = useDetachWidgetReference();
+
 	const mobileSections = useMemo(
 		() => groupWidgetsBySection(visibleWidgets, services),
 		[visibleWidgets, services],
@@ -567,10 +578,32 @@ export function Dashboard() {
 			</SectionCard>
 
 			{isMobile && mobileSections.length > 0 ? (
-				<MobileWidgetSections sections={mobileSections} onEditWidget={(id) => { setEditWidgetId(id); setWidgetDialogOpen(true); }} />
+				<MobileWidgetSections
+					sections={mobileSections}
+					onEditWidget={(id) => {
+						setEditWidgetId(id);
+						setWidgetDialogOpen(true);
+					}}
+				/>
 			) : (
 				visibleWidgets.map((widget) => (
-					<WidgetInstanceCard key={widget.id} widget={widget} onEdit={(id) => { setEditWidgetId(id); setWidgetDialogOpen(true); }} />
+					<WidgetInstanceCard
+						key={widget.id}
+						widget={widget}
+						onEdit={(id) => {
+							setEditWidgetId(id);
+							setWidgetDialogOpen(true);
+						}}
+						onCopy={
+							referencedWidgetIds.has(widget.id)
+								? () => {
+										// Detach: find the reference and clone it.
+										const ref = widgetReferences.find((r) => r.widget.id === widget.id);
+										if (ref) detachRef.mutate(ref.id);
+									}
+									: undefined
+						}
+					/>
 				))
 			)}
 
@@ -596,7 +629,10 @@ export function Dashboard() {
 			/>
 			<WidgetConfigDialog
 				open={widgetDialogOpen}
-				onClose={() => { setWidgetDialogOpen(false); setEditWidgetId(undefined); }}
+				onClose={() => {
+					setWidgetDialogOpen(false);
+					setEditWidgetId(undefined);
+				}}
 				dashboardScope="main"
 				editWidgetId={editWidgetId}
 			/>

frontend/src/pages/NamedDashboardPage.tsx

@@ -97,7 +97,14 @@ export function NamedDashboardPage() {
 			{visibleWidgets.length > 0 ? (
 				<div className="grid grid-cols-1 gap-4 md:grid-cols-2">
 					{visibleWidgets.map((widget) => (
-						<WidgetInstanceCard key={widget.id} widget={widget} onEdit={(id) => { setEditWidgetId(id); setConfigOpen(true); }} />
+						<WidgetInstanceCard
+							key={widget.id}
+							widget={widget}
+							onEdit={(id) => {
+								setEditWidgetId(id);
+								setConfigOpen(true);
+							}}
+						/>
 					))}
 				</div>
 			) : null}
@@ -125,7 +132,10 @@ export function NamedDashboardPage() {
 
 			<WidgetConfigDialog
 				open={configOpen}
-				onClose={() => { setConfigOpen(false); setEditWidgetId(undefined); }}
+				onClose={() => {
+					setConfigOpen(false);
+					setEditWidgetId(undefined);
+				}}
 				dashboardScope={dashboardScope}
 				editWidgetId={editWidgetId}
 			/>

frontend/src/pages/__tests__/Dashboard.test.tsx

@@ -24,6 +24,7 @@ vi.mock("../../hooks/useSettings", () => ({
 vi.mock("../../hooks/useWidgets", () => ({
 	useWidgetInstances: () => ({ data: [] }),
 	useWidgetReferences: () => ({ data: [] }),
+	useDetachWidgetReference: () => ({ mutate: () => {} }),
 }));
 vi.mock("../../hooks/useServices", () => ({
 	useServiceInstances: () => ({ data: [] }),

frontend/src/pages/service-tabs/OverviewTab.tsx

@@ -49,7 +49,14 @@ export function OverviewTab({ instance }: { instance: ServiceInstance }) {
 			{visibleWidgets.length > 0 ? (
 				<div className="grid grid-cols-1 gap-4 md:grid-cols-2">
 					{visibleWidgets.map((widget) => (
-						<WidgetInstanceCard key={widget.id} widget={widget} onEdit={(id) => { setEditWidgetId(id); setConfigOpen(true); }} />
+						<WidgetInstanceCard
+							key={widget.id}
+							widget={widget}
+							onEdit={(id) => {
+								setEditWidgetId(id);
+								setConfigOpen(true);
+							}}
+						/>
 					))}
 				</div>
 			) : (
@@ -72,7 +79,10 @@ export function OverviewTab({ instance }: { instance: ServiceInstance }) {
 
 			<WidgetConfigDialog
 				open={configOpen}
-				onClose={() => { setConfigOpen(false); setEditWidgetId(undefined); }}
+				onClose={() => {
+					setConfigOpen(false);
+					setEditWidgetId(undefined);
+				}}
 				serviceId={instance.id}
 				editWidgetId={editWidgetId}
 			/>