fix(cabinet): blocking screens exit via the native Telegram back button, drop the in-page Close

On a full-screen blocking overlay in the Telegram Mini App there were two exit
affordances: the native back button — which ran SPA navigation on the hidden
route underneath, so it didn't dismiss the block and kept flip-flopping between
Back and Close as the route changed — and a redundant in-page "Close" button on
the service-unavailable screen.

Make the native back button the single, stable exit: while any blocking screen
is active, TelegramBackButton shows one Back button whose click closes the Mini
App (closeTelegramApp) instead of navigating the SPA — no route change, no
Back/Close flip-flop. The normal route-based back button is restored once the
block clears. Remove the in-page Close button.

src/AppWithNavigator.tsx

@@ -15,9 +15,10 @@ import { ThemeColorsProvider } from './providers/ThemeColorsProvider';
 import { WebSocketProvider } from './providers/WebSocketProvider';
 import { ToastProvider } from './components/Toast';
 import { TooltipProvider } from './components/primitives/Tooltip';
-import { isInTelegramWebApp } from './hooks/useTelegramSDK';
+import { isInTelegramWebApp, closeTelegramApp } from './hooks/useTelegramSDK';
 import { getFallbackParentPath } from './utils/navigation';
 import { subscriptionApi } from './api/subscription';
+import { useBlockingStore } from './store/blocking';
 
 const TWEMOJI_OPTIONS = { className: 'twemoji', folder: 'svg', ext: '.svg' } as const;
 
@@ -44,6 +45,13 @@ function TelegramBackButton() {
   const pathnameRef = useRef(location.pathname);
   pathnameRef.current = location.pathname;
 
+  // A full-screen blocking overlay (maintenance / channel-sub / blacklist /
+  // account-deleted / backend-unavailable) takes over the native back button:
+  // there is nowhere to navigate, so it becomes a single, stable EXIT control.
+  const blockingType = useBlockingStore((state) => state.blockingType);
+  const blockingTypeRef = useRef(blockingType);
+  blockingTypeRef.current = blockingType;
+
   // Reliable in-app navigation depth (the app's entry point is 0). Driven by
   // React Router's navigation TYPE — NOT window.history.state.idx, which the
   // app's own redirects mutate unpredictably and which is the root flake behind
@@ -89,6 +97,15 @@ function TelegramBackButton() {
   subsCountRef.current = subsCount;
 
   useEffect(() => {
+    // On a blocking overlay, keep exactly one visible Back button (its click
+    // exits the app — see handler). Skip the route logic so it can't flip
+    // between Back and Close as the hidden route changes underneath.
+    if (blockingType) {
+      try {
+        showBackButton();
+      } catch {}
+      return;
+    }
     const isTopLevel = location.pathname === '' || BOTTOM_NAV_PATHS.includes(location.pathname);
     // Depth-independent on purpose: whether the user deep-linked in or navigated
     // here in-app, a single-tariff detail whose list just bounces back has no
@@ -103,10 +120,17 @@ function TelegramBackButton() {
         showBackButton();
       }
     } catch {}
-  }, [location, listRedirectsToDetail]);
+  }, [location, listRedirectsToDetail, blockingType]);
 
   // Stable handler — ref prevents re-subscription on every render
   const handler = useCallback(() => {
+    // A blocking overlay is a hard block with nowhere to navigate — the back
+    // button's only job is to EXIT the Mini App (no SPA navigation, so it can't
+    // flip-flop between Back and Close).
+    if (blockingTypeRef.current) {
+      closeTelegramApp();
+      return;
+    }
     // Real in-app history (depth > 0): a normal back. Otherwise we were opened
     // directly on this route via a deep-link — navigate(-1) is a no-op, so fall
     // back to a sensible parent route instead.

src/components/blocking/ServiceUnavailableScreen.tsx

@@ -4,8 +4,7 @@ import { useQueryClient } from '@tanstack/react-query';
 import { useBlockingStore } from '../../store/blocking';
 import { useFocusTrap } from '../../hooks/useFocusTrap';
 import { pingBackend, hasEverReachedBackend } from '../../api/health';
-import { isInTelegramWebApp, closeTelegramApp } from '../../hooks/useTelegramSDK';
-import { CloudWarningIcon, RestartIcon, CloseIcon } from '@/components/icons';
+import { CloudWarningIcon, RestartIcon } from '@/components/icons';
 import { Button } from '@/components/primitives';
 import { cn } from '@/lib/utils';
 import BlockingShell from './BlockingShell';
@@ -25,7 +24,6 @@ export default function ServiceUnavailableScreen() {
   const queryClient = useQueryClient();
   const [isChecking, setIsChecking] = useState(false);
   const isCheckingRef = useRef(false);
-  const inTelegram = isInTelegramWebApp();
 
   const recover = useCallback(() => {
     clearBlocking();
@@ -87,33 +85,18 @@ export default function ServiceUnavailableScreen() {
       pulse
       footer={t('blocking.serviceUnavailable.hint')}
       actions={
-        <>
-          <Button
-            variant="secondary"
-            size="lg"
-            fullWidth
-            onClick={handleRetry}
-            disabled={isChecking}
-            leftIcon={<RestartIcon className={cn('h-5 w-5', isChecking && 'animate-spin')} />}
-          >
-            {isChecking
-              ? t('blocking.serviceUnavailable.checking')
-              : t('blocking.serviceUnavailable.retry')}
-          </Button>
-          {/* Telegram Mini App only — a browser tab can't be closed by script.
-              Reliably exits the Mini App instead of routing back. */}
-          {inTelegram && (
-            <Button
-              variant="outline"
-              size="lg"
-              fullWidth
-              onClick={closeTelegramApp}
-              leftIcon={<CloseIcon className="h-5 w-5" />}
-            >
-              {t('blocking.serviceUnavailable.close')}
-            </Button>
-          )}
-        </>
+        <Button
+          variant="secondary"
+          size="lg"
+          fullWidth
+          onClick={handleRetry}
+          disabled={isChecking}
+          leftIcon={<RestartIcon className={cn('h-5 w-5', isChecking && 'animate-spin')} />}
+        >
+          {isChecking
+            ? t('blocking.serviceUnavailable.checking')
+            : t('blocking.serviceUnavailable.retry')}
+        </Button>
       }
     />
   );