feat: render admin status page preview in an iframe

The preview previously rendered the themed status page inline in the
admin document, so document-global concerns leaked in both directions:
custom CSS spilled into the admin UI and the theme body painting never
showed. Pointing the BrowserFrame at the real public URL in an iframe
isolates the CSS completely and makes the preview pixel-identical to
what visitors see. Auth for unpublished pages keeps working because the
same-origin iframe shares localStorage and the API client reads the
token from the rehydrated store.

client/src/Pages/StatusPage/Status/index.tsx

@@ -2,6 +2,7 @@ import { BasePage, BaseFallback } from "@/Components/design-elements";
 import Typography from "@mui/material/Typography";
 import { Link } from "react-router-dom";
 import Stack from "@mui/material/Stack";
+import Box from "@mui/material/Box";
 
 import { useTheme } from "@mui/material";
 import { useTranslation } from "react-i18next";
@@ -111,17 +112,9 @@ const StatusPageView = () => {
 		);
 	}
 
-	const themeConfig = THEME_CONFIGS[resolveStatusPageTheme(statusPage.theme)];
-	const themedRenderer = (
-		<BaseStatusPage
-			statusPage={statusPage}
-			monitors={monitors}
-			config={themeConfig}
-		/>
-	);
-
 	// Public route: render directly on the viewport, themed background covers everything.
 	if (isPublic) {
+		const themeConfig = THEME_CONFIGS[resolveStatusPageTheme(statusPage.theme)];
 		return (
 			<StatusPageThemeProvider
 				theme={statusPage.theme}
@@ -129,7 +122,11 @@ const StatusPageView = () => {
 				timezone={statusPage.timezone}
 				paintBody
 			>
-				{themedRenderer}
+				<BaseStatusPage
+					statusPage={statusPage}
+					monitors={monitors}
+					config={themeConfig}
+				/>
 			</StatusPageThemeProvider>
 		);
 	}
@@ -153,7 +150,16 @@ const StatusPageView = () => {
 				timezone={statusPage.timezone}
 				transparent
 			>
-				<BrowserFrame url={publicUrl}>{themedRenderer}</BrowserFrame>
+				<BrowserFrame url={publicUrl}>
+					<Box
+						component="iframe"
+						src={publicUrl}
+						title={t("pages.statusPages.preview.title")}
+						flex={1}
+						width="100%"
+						border={0}
+					/>
+				</BrowserFrame>
 			</StatusPageThemeProvider>
 		</BasePage>
 	);

client/src/Pages/StatusPage/Status/themes/BrowserFrame.tsx

@@ -64,7 +64,13 @@ export const BrowserFrame = ({ url, children }: Props) => {
 					{url}
 				</Box>
 			</Box>
-			<Box sx={{ flex: 1, minHeight: 0 }}>{children}</Box>
+			<Box
+				display="flex"
+				flexDirection="column"
+				sx={{ flex: 1, minHeight: 0 }}
+			>
+				{children}
+			</Box>
 		</Box>
 	);
 };

client/src/locales/en.json

@@ -1606,6 +1606,9 @@
 			"header": {
 				"title": "Status pages",
 				"description": "Publish public pages that show real-time uptime and incident history to your customers and stakeholders."
+			},
+			"preview": {
+				"title": "Status page preview"
 			}
 		},
 		"uptime": {