docs: refine README portfolio message

[hyeokjun32]

Summary

• Refined README structure for faster portfolio readability.
• Clarified InferEdge-Runtime as the C++ execution and result export layer.
• Synced the Korean README top summary with the same positioning.

Validation

• bash scripts/smoke_default.sh

Impact

• Makes the repository identity clearer within the first screen.
• Keeps technical details and local validation scope intact.

Notes

• No feature/API behavior changed.
• Production SaaS, DB/queue/auth/billing remain future work.