feat(docs): add NavGrid/NavCard components and restructure stage pages

- Add NavGrid.vue and NavCard.vue components for better navigation layout
- Restructure stage-0 index pages across languages into intro.md with new navigation components
- Remove old stage-0 index.md files and update stage-3 pages similarly
- Add new dependencies 'claude' and 'codex' to package.json
- Improve code formatting in multiple Vue components for better readability
- Update documentation content and structure for better user experience

docs/ja-jp/appendix/index.md

@@ -1,42 +0,0 @@
-# Appendix
-
-Knowledge base for AI, Frontend, Backend, and General Skills.
-
-## Content Overview
-
-### AI Basics
-- [Prompt Engineering](/ja-jp/appendix/prompt-engineering)
-- [AI Evolution](/ja-jp/appendix/ai-evolution)
-- [LLM Introduction](/ja-jp/appendix/llm-intro)
-- [VLM Introduction](/ja-jp/appendix/vlm-intro)
-- [AI Image Generation](/ja-jp/appendix/image-gen-intro)
-- [AI Audio Models](/ja-jp/appendix/audio-intro)
-- [Context Engineering](/ja-jp/appendix/context-engineering)
-- [AI Agents](/ja-jp/appendix/agent-intro)
-- [AI Capability Dictionary](/ja-jp/appendix/ai-capability-dictionary)
-
-### Frontend Development
-- [Web Basics (HTML/CSS/JS)](/ja-jp/appendix/web-basics)
-- [Frontend Evolution](/ja-jp/appendix/frontend-evolution)
-- [Frontend Performance](/ja-jp/appendix/frontend-performance)
-- [Canvas 2D](/ja-jp/appendix/canvas-intro)
-- [URL to Browser](/ja-jp/appendix/url-to-browser)
-- [Browser DevTools](/ja-jp/appendix/browser-devtools)
-
-### Backend Development
-- [Backend Evolution](/ja-jp/appendix/backend-evolution)
-- [Backend Languages](/ja-jp/appendix/backend-languages)
-- [Database Principles](/ja-jp/appendix/database-intro)
-- [Cache Design](/ja-jp/appendix/cache-design)
-- [Message Queues](/ja-jp/appendix/queue-design)
-- [Authentication](/ja-jp/appendix/auth-design)
-- [Tracking Design](/ja-jp/appendix/tracking-design)
-- [Operations](/ja-jp/appendix/operations)
-
-### General Skills
-- [API Introduction](/ja-jp/appendix/api-intro)
-- [IDE Introduction](/ja-jp/appendix/ide-intro)
-- [Terminal Introduction](/ja-jp/appendix/terminal-intro)
-- [Git Introduction](/ja-jp/appendix/git-intro)
-- [Computer Networks](/ja-jp/appendix/computer-networks)
-- [Deployment](/ja-jp/appendix/deployment)