FIX: Enable scrollbars in CodeMirror editors and complete missing i18n

CodeMirror Scrollbar Fixes:
- Add EditorView.theme configurations with overflow: auto for .cm-scroller
- Configure scrollPastEnd: false in basicSetup for all CodeMirror instances
- Fix FileViewer, CredentialEditor, HostManagerEditor, and FileManagerFileEditor
- Ensure proper height: 100% styling for editor containers

i18n Completion:
- Add missing "movedItems" translation key for file move operations
- English: "Moved {{count}} items"
- Chinese: "已移动 {{count}} 个项目"

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

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

src/locales/en/translation.json

@@ -737,6 +737,7 @@
     "deleteFiles": "Delete {{count}} items",
     "filesCopiedToClipboard": "{{count}} items copied to clipboard",
     "filesCutToClipboard": "{{count}} items cut to clipboard",
+    "movedItems": "Moved {{count}} items",
     "failedToDeleteItem": "Failed to delete item",
     "itemRenamedSuccessfully": "{{type}} renamed successfully",
     "failedToRenameItem": "Failed to rename item",