fix: comprehensive repo audit — 15 issues fixed

fix: self-audit — 7 issues found and corrected

feat: Sprint 4 — indexed search + job rate limiting

fix: Sprint 1b — null deref, supports_vision, empty response logging, test

feat(schemas): IIIF-native Sprint 1 — schema evolution for streaming architecture

fix(backend): Sprint Fix 2 — data integrity, error handling, robustness

fix(sprint-f1): sécurité — path traversal, SSRF, CORS, validation inputs

feat(sprint6-B): validation éditoriale + recherche plein texte

feat(sprint4-session-a): API FastAPI — structure de base + endpoints lecture et export