docs(gh-pages): refresh documentation with domain-verified accuracy

[if414013]

Summary

• Updated 7 gh-pages docs to reflect recent changes: provider enable/disable toggle (fix(web-ui): add provider enable/disable toggle for admin users #188), model visibility defaults (feat(model): add admin-configurable model visibility filtering #183), OAuth relay (feat(proxy): add OAuth relay support for gateway mode #185), and proxy fixes
• All updates cross-checked by 6 domain agents (backend, frontend, database, devops, backend-qa, frontend-qa)
• 57 insertions, 47 deletions across api-reference, web-ui, modules, architecture/index, request-flow, deployment, and configuration

Files Updated

File	Changes
api-reference.md	Added provider toggle and model visibility endpoints
web-ui.md	Added provider toggle and model visibility admin features
modules.md	Added proxy_token_manager and model visibility modules
architecture/index.md	Fixed AppState fields, streaming pipeline labels
architecture/request-flow.md	Fixed streaming parser references (Binary → SseParser)
deployment.md	Fixed database table names to match source
configuration.md	Fixed provider_settings table reference

Test plan

• Verify Jekyll builds gh-pages site without errors
• Spot-check updated docs against source code
• Confirm no broken internal links

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