v0.3.3 security hardening

[Rcloudso]

Product impact

Strengthens the v0.3.3 deployment and public API security boundary without changing the FAQ-first product direction or SSE compatibility surface. Production now fails closed on unsafe credentials, public endpoints reject oversized or malformed inputs, anonymous conversation access remains owner-bound, and rendered/exported output is hardened against injection.

Implementation scope

• validate production admin/JWT/provider configuration and document secure deployment defaults
• add bounded public FAQ DTOs, concurrency control, and safer rate-limit behavior
• preserve anonymous session ownership across conversation and analytics workflows
• mask model credentials and prevent blank/placeholder secrets from being persisted
• harden Markdown links, CSV exports, database cleanup, logs, and error responses
• enforce OCR request, image, document, and parsed-content limits
• add bilingual operator guidance, v0.3.3 release notes, evidence, and security review records
• add focused deployment, public API, analytics, output, OCR, retry, and E2E regressions

Verification

• EMBED_PROVIDER=other npm test
• EMBED_PROVIDER=other npm run eval:faq — 11/11; Top1 100%, Top3 100%, no-match 100%
• PLAYWRIGHT_CHANNEL=chromium npm run test:e2e — 48/48
• EMBED_PROVIDER=other npm run build — passed (5,320 modules)
• OCR unit suite — 11/11; Python compile checks passed
• git diff --check
• Codex Security final diff scan — 31/31 coverage, 0 open findings after remediation

Remaining risks

• The Docker OCR restart integration scenario was not rerun; OCR contract behavior was covered by direct unit tests.
• npm audit reports a React Router RSC/server-action advisory in the dependency graph; this Vite BrowserRouter SPA does not expose the affected RSC/server-action path. Applicability and reasoning are documented in the security review.