Feat: add Traditional Chinese localization

[k306lclc]

Summary

Add a complete Traditional Chinese localization for the Taskboard Web UI, server and launcher messages, Codex and WorkBuddy injection surfaces, and Tauri packaging metadata.

Changes

• switch the Chinese locale from zh-CN to zh-TW and keep the document language synchronized
• translate app-owned UI, accessibility labels, server errors, automation prompts, injector text, and native launcher dialogs into Traditional Chinese
• add README.zh-TW.md and link it from the existing READMEs
• retain Simplified Chinese host-label aliases and the legacy persisted 改进 label for compatibility
• update tests to assert the Traditional Chinese product contract

Testing

• npm run typecheck
• npm test: 362 passed, 1 Windows-only skipped; component tests 9 passed
• npm run app:build
• npm run app:preflight --
• npm run app:verify-packaged-taskctl --
• strict deep codesign verification on the built and installed universal macOS app
• packaged runtime inspection with lang=zh-TW covering the board, project menu, and create-issue dialog

Risk

Medium. The change is broad in visible copy and native launcher messages, but functional changes are limited to locale metadata and compatibility aliases. No release, notarization, migration, or external service operation is included.