fix: move tutorial assets to public directory and rename file

- Rename 5min-quickstart-en.md to 001_5min-agent-quickstart-en.md for better ordering
- Move openapi.png from src/pages/assets/ to public/assets/ following Astro best practices
- Static assets in public/ directory are served directly without build processing

Author: vincentbergman

public/assets/openapi.png

@@ -198,7 +198,7 @@ You can see the following key information from the logs:
 
 Additionally, we provide OpenAPI documentation and debugging interface based on the FastAPI framework, which you can access at: [http://localhost:8000/docs](http://localhost:8000/docs)
 
-<img src="./openapi.png" style="width:600px;height:400px;">
+<img src="/assets/openapi.png" style="width:600px;height:400px;">
 
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@@ -655,5 +655,3 @@ Congratulations on completing the NetDriver quickstart! Here's what you can do n
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 **Author**: Vincent Bergman
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