FIX: Complete internationalization for text and code editors

Missing i18n Fixes:
- Replace "Unknown size" with t("fileManager.unknownSize")
- Replace "File is empty" with t("fileManager.fileIsEmpty")
- Replace "Modified:" with t("fileManager.modified")
- Replace "Large File Warning" with t("fileManager.largeFileWarning")
- Replace file size warning message with t("fileManager.largeFileWarningDesc")

Credential Editor i18n:
- Replace "Invalid Key" with t("credentials.invalidKey")
- Replace "Detection Error" with t("credentials.detectionError")
- Replace "Unknown" with t("credentials.unknown")

Translation Additions:
- English: unknownSize, fileIsEmpty, modified, largeFileWarning, largeFileWarningDesc
- English: invalidKey, detectionError, unknown for credentials
- Chinese: corresponding translations for all new keys

Technical Improvements:
- Update formatFileSize function to accept translation function parameter
- Ensure proper translation interpolation for dynamic content

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/locales/zh/translation.json

@@ -149,7 +149,10 @@
     "generateRSA": "生成 RSA",
     "keyPairGeneratedSuccessfully": "{{keyType}} 密钥对生成成功",
     "failedToGenerateKeyPair": "生成密钥对失败",
-    "generateKeyPairNote": "直接生成新的SSH密钥对。这将替换表单中的现有密钥。"
+    "generateKeyPairNote": "直接生成新的SSH密钥对。这将替换表单中的现有密钥。",
+    "invalidKey": "无效密钥",
+    "detectionError": "检测错误",
+    "unknown": "未知"
   },
   "sshTools": {
     "title": "SSH 工具",
@@ -761,6 +764,11 @@
     "filesCopiedToClipboard": "{{count}} 个项目已复制到剪贴板",
     "filesCutToClipboard": "{{count}} 个项目已剪切到剪贴板",
     "movedItems": "已移动 {{count}} 个项目",
+    "unknownSize": "未知大小",
+    "fileIsEmpty": "文件为空",
+    "modified": "修改时间",
+    "largeFileWarning": "大文件警告",
+    "largeFileWarningDesc": "此文件大小为 {{size}}，以文本形式打开可能会导致性能问题。",
     "failedToDeleteItem": "删除项目失败",
     "itemRenamedSuccessfully": "{{type}}重命名成功",
     "failedToRenameItem": "重命名项目失败",