docs: complete brownfield reference documentation (#170) #219

Job	Run time
OSV-Scanner (SCA)	6s
Semgrep (SAST)	24s
jscpd (duplication < 3% on touched code)	12s
Gitleaks (secret scan)	13s
Trivy (filesystem + container scan)	18s
SBOM (SPDX + CycloneDX)	21s
	1m 34s

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