Secures 20 mutating routes across 7 files against path traversal, shell injection, and ReDoS vectors: - containers.js: container ID validation + resource limit bounds (6 routes) - recipes/manage.js: recipe ID slug validation (4 routes) - tailscale.js: subdomain regex before interpolation + shell char blocking (2) - workflows.js: workflow ID slug validation (3 routes) - dependencies.js: service ID + dependsOn array validation (3 routes) - logs.js: YYYY-MM-DD date format validation (1 route) - sites.js: additional domain validation (1 route) Uses existing REGEX patterns from constants.js. No new dependencies. Codex: B (no blocking issues, 4 Low follow-ups for tests + strict bools). 1552/1552 tests pass, 0 regressions.