feat(telemetry): add per-signal ingest E2E latency histogram (#63) #78

Job	Run time
jscpd (duplication < 3% on touched code)	16s
OSV-Scanner (SCA)	5s
Trivy (filesystem + container scan)	17s
Semgrep (SAST)	32s
SBOM (SPDX + CycloneDX)	25s
Gitleaks (secret scan)	18s
	1m 53s

Provide feedback