docs: refine README portfolio message

[hyeokjun32]

Summary

• Refined README structure for faster portfolio readability.
• Reduced duplicated positioning text and clarified the main InferEdgeLab message.
• Moved Local Studio into a recommended demo entry point.

Validation

• poetry run python3 -m pytest -q
• bash scripts/demo_pipeline_full.sh --help

Impact

• Improves first impression for recruiters/interviewers.
• Makes the project identity clear within the first screen.
• Keeps the technical evidence and local-first scope intact.

Notes

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