Add a public README with diagrams and screenshots #6

Job	Run time
CodeQL security scan (python)	40s
CodeQL security scan (javascript-typescript)	37s
Dependency audit (pip-audit)	36s
Secret scan (gitleaks)	7s
Backend (lint + type + test)	1m 42s
Frontend (lint + test)	1m 30s
	5m 12s

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