fix(docker): добавить переменную окружения для внутреннего URL бэкенда

lib/data-source.tsx

@@ -59,9 +59,13 @@ function normalizeBackendUrl(url: string): string {
 }
 
 export function DataSourceProvider({ children }: { children: React.ReactNode }) {
-  const [mode, setModeState] = useState<DataSourceMode>(defaultDataSourceMode)
-  const [backendUrl, setBackendUrlState] = useState(LOCAL_DEFAULT_BACKEND_URL)
-  const [prefsHydrated, setPrefsHydrated] = useState(false)
+  const [mode, setModeState] = useState<DataSourceMode>(() =>
+    typeof window === "undefined" ? defaultDataSourceMode() : readStoredMode(),
+  )
+  const [backendUrl, setBackendUrlState] = useState(() =>
+    typeof window === "undefined" ? LOCAL_DEFAULT_BACKEND_URL : readStoredBackendUrl(),
+  )
+  const [prefsHydrated, setPrefsHydrated] = useState(() => typeof window !== "undefined")
   const [backendStatus, setBackendStatus] = useState<boolean | undefined>(undefined)
   const backendUrlLocked = isBackendUrlLocked()
   const mockModeAvailable = isMockDataSourceAvailable()
@@ -91,9 +95,12 @@ export function DataSourceProvider({ children }: { children: React.ReactNode })
   }, [backendUrlLocked])
 
   const checkBackend = useCallback(async () => {
-    const url = normalizeBackendUrl(backendUrl)
+    const healthUrl =
+      configuredBackendUrl().kind === "same-origin"
+        ? "/health"
+        : `${normalizeBackendUrl(backendUrl)}/health`
     try {
-      const res = await fetch(`${url}/health`, { signal: AbortSignal.timeout(3000) })
+      const res = await fetch(healthUrl, { signal: AbortSignal.timeout(3000) })
       setBackendStatus(res.ok)
     } catch {
       setBackendStatus(false)