[GDPR] S4:F2: File storage at rest is unencrypted; cloud relies entirely on infra disk encryption

[2witstudios]

Finding ID: S4:F2 (Stream 4 uses F1–F16 numbering; this ID corresponds to section ### F2 in the stream doc)
Stream: 4
Severity: critical
GDPR article(s): Art 32(1)(a), Art 25
Deployment modes: onprem,tenant
Location: apps/processor/src/cache/content-store.ts

File storage at rest is unencrypted; cloud relies entirely on infra disk encryption

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See docs/security/gdpr-audit/04-minimization-breach.md for current behavior, gap analysis, recommendation, and any sub-findings.