feat: add ButtonsTab for per-section button style customization

Visual editor in admin settings for configuring Telegram button colors
and custom emoji IDs per menu section. Includes API client, draft state
management, save/reset, and translations for ru/en/fa/zh locales.

src/locales/zh.json

@@ -973,6 +973,7 @@
       "noSearchResults": "未找到结果",
       "example": "示例",
       "analytics": "分析",
+      "buttons": "按钮",
       "notConfigured": "未配置",
       "counterActive": "已启用",
       "counterInactive": "未启用",
@@ -1033,6 +1034,35 @@
       "resetAllColors": "重置所有颜色",
       "statusColors": "状态颜色"
     },
+    "buttons": {
+      "color": "按钮颜色",
+      "emojiId": "自定义表情 ID",
+      "emojiPlaceholder": "自定义表情 ID（可选）",
+      "resetAll": "重置所有样式",
+      "sections": {
+        "home": "主页",
+        "subscription": "订阅",
+        "balance": "余额",
+        "referral": "推荐",
+        "support": "支持",
+        "info": "信息",
+        "admin": "管理面板"
+      },
+      "descriptions": {
+        "home": "个人中心按钮",
+        "subscription": "订阅管理",
+        "balance": "充值和余额",
+        "referral": "推荐计划",
+        "support": "支持工单",
+        "info": "信息板块",
+        "admin": "网页管理面板"
+      },
+      "styles": {
+        "primary": "蓝色",
+        "success": "绿色",
+        "danger": "红色"
+      }
+    },
     "apps": {
       "title": "应用管理",
       "addApp": "添加应用",