* feat: add doubao provider and ByteDance sponsorship
- Add doubao provider using DeepSeek SDK with Volcengine base URL
- Add ByteDance Doubao sponsorship acknowledgment to about pages
- Update all README files (EN/CN/JA) with K2-thinking model info
- Update ai-providers.md with doubao configuration
- Keep both gateway and doubao providers after merge
* style: auto-format with Biome
* feat: add doubao and sglang to provider config panel
* fix: add doubao and sglang to validate-model API and logo maps
* docs: update ByteDance sponsorship note in all README versions
* docs: add Doubao logo to sponsorship note
* fix: use raw GitHub URL for Doubao logo in READMEs
* fix: separate link and image in sponsorship note
* fix: use PNG instead of SVG for Doubao logo
* fix: use current branch for PNG URL (will update to main after merge)
* docs: reorganize Deployment section and update image URLs to main
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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
- Use fixed port 61337 in production instead of random ports (10000-65535)
- localStorage is origin-specific, so random ports caused settings loss
- Add locale save/restore since language is URL-based
- Fixes#399