docs: correct the development and logging pages against the Vite proxy, the build config and the JSON log formatters

[silentoplayz]

Summary

I compared the development and logging pages with the frontend build config, the dev scripts and the log formatters.

• Development: package.json allows Node.js up to 22.x, and the locked dependencies (pdfjs-dist among them) need 20.19 or later, so the requirement is 20.19+ on Node 20 or 22.13+ on Node 22 rather than 22.10 and up. The LAN-testing steps keep the CORS_ALLOW_ORIGIN step: the Vite dev server proxies /api, /ollama, /openai, /oauth and /ws, but Socket.IO still checks the browser's Origin against that list (WEBUI_BACKEND_URL points the proxy elsewhere). Ports are changed with PORT and npm run dev:5050 (plus that port's origin in CORS_ALLOW_ORIGIN), not by editing config files. With no backend, the page redirects to a "Backend Required" error page rather than waiting, and /docs is served only with ENV=dev.
• Logging: production builds strip console.log, console.debug and console.error unless built with ENV=dev, so the frontend section now says so. The JSON error field is an object with type, message and stacktrace, and the top-level stacktrace only appears on the few lines written before the Loguru sink starts. An unrecognised GLOBAL_LOG_LEVEL falls back to INFO, and SRC_LOG_LEVELS is a legacy placeholder.

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: package.json (engines, scripts), vite.config.ts (proxy, esbuild.pure), backend/dev.sh, main.py (docs_url), src/routes/+layout.svelte and src/routes/error/+page.svelte, utils/logger.py, and env.py (JSONFormatter, GLOBAL_LOG_LEVEL, SRC_LOG_LEVELS).