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/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"