fix: 修复代理编辑页面翻译问题和代理卡密生成页面

- 添加 admin.agents.create.saveBtn 和 admin.agents.editSuccess 翻译
- 修复代理卡密生成页面API路径错误，使用/agent/apps/{id}获取卡类
- 重构代理卡密生成页面样式，参考管理员后台卡密生成页面
- 添加代理卡密生成页面完整i18n国际化支持

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/plugins/i18n/en.json

@@ -1322,8 +1322,11 @@
         "passwordMinLength": "Password must be at least 6 characters",
         "createSuccess": "Agent created successfully",
         "createFailed": "Failed to create agent",
-        "cancel": "Cancel"
+        "cancel": "Cancel",
+        "saveBtn": "Save Changes"
       },
+      "editSuccess": "Agent updated successfully",
+      "editFailed": "Failed to update agent",
       "enable": "Enable",
       "disable": "Disable",
       "deleteAgent": "Delete Agent",
@@ -1341,7 +1344,8 @@
         "save": "Save",
         "usernameHint": "Username cannot be changed",
         "passwordPlaceholder": "Leave empty to keep current password",
-        "passwordHint": "Enter new password to change, leave empty to keep current"
+        "passwordHint": "Enter new password to change, leave empty to keep current",
+        "saveBtn": "Save Changes"
       }
     },
     "announcements": {
@@ -2857,7 +2861,27 @@
         "estimatedCost": "Estimated Cost",
         "cancel": "Cancel",
         "generating": "Generating...",
-        "generateBtn": "Generate Cards"
+        "generateBtn": "Generate Cards",
+        "selectAppFirst": "Please select an application first",
+        "selectCardTypeFirst": "Please select a card type first",
+        "countRange": "Quantity must be between 1 and 100",
+        "config": "Generation Config",
+        "configDesc": "Select authorized application and available card type, set quantity",
+        "application": "Select Application",
+        "selectApplication": "Please select an application",
+        "cardType": "Select Card Type",
+        "selectCardType": "Please select a card type",
+        "noCardType": "No available card types for this application",
+        "count": "Quantity",
+        "maxCount": "Maximum 100 cards per generation",
+        "preview": "Generation Preview",
+        "app": "Application",
+        "type": "Card Type",
+        "unitPrice": "Unit Price",
+        "quantity": "Quantity",
+        "units": "cards",
+        "totalAmount": "Estimated Cost",
+        "generateNow": "Generate Now"
       }
     }
   },