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/tailwind.config.ts

@@ -0,0 +1,57 @@
+import type { Config } from 'tailwindcss';
+import type { DefaultColors } from 'tailwindcss/types/generated/colors';
+
+const themeDark = (colors: DefaultColors) => ({
+  50: '#0d1117',
+  100: '#161b22',
+  200: '#21262d',
+  300: '#30363d',
+});
+
+const themeLight = (colors: DefaultColors) => ({
+  50: '#ffffff',
+  100: '#f6f8fa',
+  200: '#e8edf1',
+  300: '#d0d7de',
+});
+
+const config: Config = {
+  content: [
+    './src/pages/**/*.{js,ts,jsx,tsx,mdx}',
+    './src/components/**/*.{js,ts,jsx,tsx,mdx}',
+    './src/app/**/*.{js,ts,jsx,tsx,mdx}',
+  ],
+  darkMode: 'class',
+  theme: {
+    extend: {
+      borderColor: ({ colors }) => {
+        return {
+          light: themeLight(colors),
+          dark: themeDark(colors),
+        };
+      },
+      colors: ({ colors }) => {
+        const colorsDark = themeDark(colors);
+        const colorsLight = themeLight(colors);
+
+        return {
+          dark: {
+            primary: colorsDark[50],
+            secondary: colorsDark[100],
+            ...colorsDark,
+          },
+          light: {
+            primary: colorsLight[50],
+            secondary: colorsLight[100],
+            ...colorsLight,
+          },
+        };
+      },
+    },
+  },
+  plugins: [
+    require('@tailwindcss/typography'),
+    require('@headlessui/tailwindcss')({ prefix: 'headless' }),
+  ],
+};
+export default config;