docs: add CSV export formula-injection handling guidance

Document that provider CSV exports should be handled with formula-injection safety when opened in spreadsheet tooling.

README.md

@@ -133,6 +133,7 @@ This wrapper now delegates to `BlackWall\Auth\AuthClient`.
 - Register only HTTPS redirect URIs in provider client settings (HTTP should be used only for localhost loopback during development).
 - Use OAuth/portal authentication endpoints for end users; provider admin login endpoints enforce separate admin scope checks.
 - For provider admin enrollment URL export operations, use `POST` with CSRF protection; do not automate them via unauthenticated `GET` links.
+- Handle provider CSV exports with formula-injection safety in mind if opening them in spreadsheet applications.
 - Never place client secrets, refresh tokens, or access tokens in URL query strings.
 - For OIDC providers, include a per-request `nonce` in authorisation requests.
 - For direct Cryptbin API usage, send `key_b64url` on unwrap calls; provider rejects key-mismatch unwrap attempts with `403 Forbidden`.

docs/INTEGRATION_GUIDE.md

@@ -152,6 +152,7 @@ Provider user/project assignment views may exclude disabled projects even if his
 - Use exactly one client authentication method per token/control request (do not send both HTTP Basic and `client_secret` form fields together).
 - If you call provider WebAuthn login challenge/verify endpoints directly, use `POST` only.
 - Treat admin enrollment URL export as a state-changing operation: call it with `POST` and include a valid CSRF token.
+- Treat provider CSV exports as untrusted input in spreadsheet tools; prefer importing into systems that neutralise formula cells.
 - Configure OAuth client redirect URIs as HTTPS in production; reserve HTTP for localhost loopback testing only.
 - Assume provider rate limits are enforced per source identity (for example IP) and shared across related auth endpoints.
 - Treat report/export-style provider endpoints as high-cost and expect stricter rate limits.