feat: add 'no color' option for button style customization

Adds a 'default' style option that removes color from buttons, showing
Telegram's native default style. Updates type, UI chip, preview, and
translations for all 4 locales.

src/api/buttonStyles.ts

@@ -1,7 +1,7 @@
 import apiClient from './client';
 
 export interface ButtonSectionConfig {
-  style: 'primary' | 'success' | 'danger';
+  style: 'primary' | 'success' | 'danger' | 'default';
   icon_custom_emoji_id: string;
 }
 

src/components/admin/ButtonsTab.tsx

@@ -9,9 +9,10 @@ import {
   ButtonSection,
 } from '../../api/buttonStyles';
 
-type StyleValue = 'primary' | 'success' | 'danger';
+type StyleValue = 'primary' | 'success' | 'danger' | 'default';
 
 const STYLE_OPTIONS: { value: StyleValue; colorClass: string }[] = [
+  { value: 'default', colorClass: 'bg-dark-500' },
   { value: 'primary', colorClass: 'bg-blue-500' },
   { value: 'success', colorClass: 'bg-green-500' },
   { value: 'danger', colorClass: 'bg-red-500' },
@@ -134,12 +135,14 @@ export function ButtonsTab() {
                 </div>
                 {/* Live preview chip */}
                 <div
-                  className={`rounded-lg px-3 py-1.5 text-xs font-medium text-white ${
-                    cfg.style === 'success'
-                      ? 'bg-green-500'
-                      : cfg.style === 'danger'
-                        ? 'bg-red-500'
-                        : 'bg-blue-500'
+                  className={`rounded-lg px-3 py-1.5 text-xs font-medium ${
+                    cfg.style === 'default'
+                      ? 'bg-dark-600 text-dark-300'
+                      : cfg.style === 'success'
+                        ? 'bg-green-500 text-white'
+                        : cfg.style === 'danger'
+                          ? 'bg-red-500 text-white'
+                          : 'bg-blue-500 text-white'
                   }`}
                 >
                   {t(`admin.buttons.styles.${cfg.style}`)}

src/locales/en.json

@@ -1311,6 +1311,7 @@
         "admin": "Web admin panel"
       },
       "styles": {
+        "default": "No color",
         "primary": "Blue",
         "success": "Green",
         "danger": "Red"

src/locales/fa.json

@@ -1020,6 +1020,7 @@
         "admin": "پنل مدیریت وب"
       },
       "styles": {
+        "default": "بدون رنگ",
         "primary": "آبی",
         "success": "سبز",
         "danger": "قرمز"

src/locales/ru.json

@@ -1826,6 +1826,7 @@
         "admin": "Веб-админка"
       },
       "styles": {
+        "default": "Без цвета",
         "primary": "Синий",
         "success": "Зелёный",
         "danger": "Красный"

src/locales/zh.json

@@ -1058,6 +1058,7 @@
         "admin": "网页管理面板"
       },
       "styles": {
+        "default": "无颜色",
         "primary": "蓝色",
         "success": "绿色",
         "danger": "红色"