feat: монорепо миграция, Discover/SearxNG улучшения

- Миграция на монорепозиторий (apps/frontend, apps/chat-service, etc.)
- Discover: проверка SearxNG, понятное empty state при ненастроенном поиске
- searxng.ts: валидация URL, проверка JSON-ответа, авто-добавление http://
- docker/searxng-config: настройки для JSON API SearxNG

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/frontend/src/components/ChatWindow.tsx

@@ -0,0 +1,76 @@
+'use client';
+
+import Navbar from './Navbar';
+import Chat from './Chat';
+import EmptyChat from './EmptyChat';
+import NextError from 'next/error';
+import { useChat } from '@/lib/hooks/useChat';
+import SettingsButtonMobile from './Settings/SettingsButtonMobile';
+import { Block } from '@/lib/types';
+import Loader from './ui/Loader';
+
+export interface BaseMessage {
+  chatId: string;
+  messageId: string;
+  createdAt: Date;
+}
+
+export interface Message extends BaseMessage {
+  backendId: string;
+  query: string;
+  responseBlocks: Block[];
+  status: 'answering' | 'completed' | 'error';
+}
+
+export interface File {
+  fileName: string;
+  fileExtension: string;
+  fileId: string;
+}
+
+export interface Widget {
+  widgetType: string;
+  params: Record<string, any>;
+}
+
+const ChatWindow = () => {
+  const { hasError, notFound, messages, isReady } = useChat();
+
+  if (hasError) {
+    return (
+      <div className="relative">
+        <div className="absolute w-full flex flex-row items-center justify-end mr-5 mt-5">
+          <SettingsButtonMobile />
+        </div>
+        <div className="flex flex-col items-center justify-center min-h-screen">
+          <p className="dark:text-white/70 text-black/70 text-sm">
+            Failed to connect to the server. Please try again later.
+          </p>
+        </div>
+      </div>
+    );
+  }
+
+  return isReady ? (
+    notFound ? (
+      <NextError statusCode={404} />
+    ) : (
+      <div>
+        {messages.length > 0 ? (
+          <>
+            <Navbar />
+            <Chat />
+          </>
+        ) : (
+          <EmptyChat />
+        )}
+      </div>
+    )
+  ) : (
+    <div className="flex items-center justify-center min-h-screen w-full">
+      <Loader />
+    </div>
+  );
+};
+
+export default ChatWindow;