docs: add Beszel, SQLite backup, and Custom widgets documentation (#5930)

apps/docs/docs/widgets/custom-api/index.mdx

@@ -0,0 +1,29 @@
+---
+title: 'Custom API'
+description: 'Displays data from a custom API endpoint using configurable display types and optional JSX templates.'
+hide_title: true
+---
+
+import { WidgetHeader } from '@site/src/components/widgets/header';
+import { AddingWidget } from '@site/src/components/widgets/adding';
+import { customApiWidget } from '.';
+
+
+<WidgetHeader
+  widget={customApiWidget}
+  categories={['Custom', 'API']}
+/>
+
+This widget fetches data from a custom API endpoint defined in [Custom Widgets management](/docs/management/custom-widgets) and renders it using configurable display types.
+
+Custom API widgets are created and configured through the admin management page. Each widget definition specifies the API endpoint, authentication, display type, and refresh interval.
+
+See the [Custom Widgets documentation](/docs/management/custom-widgets) for full details on creating and configuring custom widgets.
+
+### Adding the widget
+
+<AddingWidget />
+
+:::note
+Custom API widgets must first be created in **Management → Custom Widgets** before they appear in the widget picker.
+:::

apps/docs/docs/widgets/custom-api/index.ts

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+import { WidgetDefinition } from "@site/src/types";
+import { IconApi } from "@tabler/icons-react";
+
+export const customApiWidget: WidgetDefinition = {
+  icon: IconApi,
+  name: "Custom API",
+  description: "Displays data from a custom API endpoint using configurable display types and optional JSX templates.",
+  path: "../../widgets/custom-api",
+};