refactor(widgets): stabilize widget components after useQuery migration

Add WidgetEmptyState component for widgets that need a loading fallback.
Disable refetch-on-mount/focus/reconnect and retry for integration widgets
so cached data is preserved. Ensure hooks are never called conditionally.

packages/widgets/src/app/component.tsx

@@ -3,7 +3,7 @@
 import type { PropsWithChildren } from "react";
 import { Fragment, Suspense } from "react";
 import { Flex, rem, Stack, Text, Tooltip, UnstyledButton } from "@mantine/core";
-import { IconLoader } from "@tabler/icons-react";
+import { IconMinus } from "@tabler/icons-react";
 import combineClasses from "clsx";
 
 import { clientApi } from "@homarr/api/client";
@@ -13,6 +13,7 @@ import { useRegisterSpotlightContextResults } from "@homarr/spotlight";
 import { useI18n } from "@homarr/translation/client";
 import { MaskedOrNormalImage } from "@homarr/ui";
 
+import { WidgetEmptyState } from "../common/empty-state";
 import type { WidgetComponentProps } from "../definition";
 import classes from "./app.module.css";
 import { PingDot } from "./ping/ping-dot";
@@ -55,7 +56,7 @@ export default function AppWidget({ options, isEditMode, height, width }: Widget
     [app, options.openInNewTab],
   );
 
-  if (!app) return null;
+  if (!app) return <WidgetEmptyState />;
 
   const isTiny = height < 100 || width < 100;
   const isColumnLayout = options.layout.startsWith("column");
@@ -131,7 +132,7 @@ export default function AppWidget({ options, isEditMode, height, width }: Widget
         </Flex>
       </Tooltip.Floating>
       {options.pingEnabled && !settings.forceDisableStatus && !board.disableStatus && app.href ? (
-        <Suspense fallback={<PingDot icon={IconLoader} color="blue" tooltip={`${t("common.action.loading")}…`} />}>
+        <Suspense fallback={<PingDot icon={IconMinus} color="gray" tooltip={`${t("common.action.loading")}…`} />}>
           <PingIndicator appId={app.id} />
         </Suspense>
       ) : null}