Module: MongoDB Documentation & UX Polish

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Finalize all documentation, internationalization, and user-experience refinements for the MongoDB feature set.

Scope

• Documentation: Update README.md and any in-app help to cover MongoDB connection setup, query usage, and known limitations
• i18n audit: Ensure all MongoDB-related UI strings are properly translated in enUS.ts and zhCN.ts; verify no hardcoded strings remain
• UX review & polish:
  • Consistent loading states across all MongoDB flows (connecting, querying, browsing)
  • Empty states for no databases, no collections, no results
  • Error message quality and actionability
  • Keyboard shortcuts and accessibility review
• Testing: End-to-end test coverage for the full MongoDB workflow (connect → browse → query → results)
• Security: Verify credentials are stored securely via Tauri's store; no sensitive data leaks in logs

Key files to create/modify

• README.md
• src/lang/enUS.ts, src/lang/zhCN.ts
• All MongoDB view components (UX audit)
• tests/ (new test files)

Acceptance criteria

• README documents MongoDB support with setup instructions
• All UI strings are in i18n files with English and Chinese translations
• Loading, empty, and error states are polished and consistent
• End-to-end tests cover the MongoDB workflow
• No sensitive credentials exposed in logs or dev tools

Parent issue: #112
Depends on: Module: MongoDB Schema & Collection Browsing