docs: correct the enterprise pages' SSO, MFA, Redis, OpenTelemetry, health check and image tag claims

[silentoplayz]

Summary

I checked the technical claims on the enterprise pages against the code. Positioning and pricing text is untouched.

• SSO: there is no SAML support. The code registers Google, Microsoft, GitHub, Feishu and a generic OIDC provider, so the two pages now say OIDC and OAuth 2.0 providers.
• MFA: Open WebUI has none of its own. It is whatever the identity provider enforces through SSO.
• Redis: configuration is shared through the database, not Redis. Redis carries WebSocket coordination, token revocation and shared caches.
• OpenTelemetry: ENABLE_OTEL=true exports nothing on its own, so the per-signal switches are added. The endpoint example now uses gRPC port 4317, which matches the default exporter, and OTEL_OTLP_SPAN_EXPORTER=http is named for HTTP port 4318.
• Health checks: /api/models needs a user token (API keys are off by default), and /ready is documented as the readiness probe.
• Image tags: :main follows the release branch and doubles as :latest, while :dev is the development build.
• Audit logging is off by default and goes to DATA_DIR/audit.log unless ENABLE_AUDIT_STDOUT is set.

Related issue or discussion

None.

Checklist

• I have reviewed the relevant documentation and matched the existing style.
• This PR meets Open WebUI's contribution standards: it is accurate, relevant to users, narrowly scoped, maintainable, and not promotional content, advertising, lead generation, SEO placement, or a request to list a product, service, provider, integration, gateway, tool, or company primarily for visibility.
• I understand that PRs that do not meet these standards may be closed without review and will not be merged. Repeated, low-quality, off-topic, promotional, or intentionally misleading submissions may result in the contributor being blocked from future participation in Open WebUI repositories.

Notes for reviewers

Sources on dev: config.py (load_oauth_providers, ENABLE_API_KEYS), a repository search for saml, totp and mfa outside i18n, models/config.py, env.py (ENABLE_OTEL*, OTEL_OTLP_SPAN_EXPORTER, AUDIT_*), utils/telemetry/setup.py, main.py (/api/models, /ready), and .github/workflows/docker.yaml.