赵月辉 / fastgpt-migrated

* feat: add Gemini 3.1 models

- Add gemini-3.1-pro-preview (released February 19, 2026)
- Add gemini-3.1-flash-lite-preview (released March 3, 2026)

Both models support:
- 1M context window
- 64k max response
- Vision
- Tool choice

* docs: switch to docs layout and apply black theme

- Change layout from notebook to docs
- Update logo to icon + text format
- Apply fumadocs black theme
- Simplify global.css (keep only navbar and TOC styles)
- Fix icon components to properly accept className props
- Add mobile text overflow handling
- Update Node engine requirement to >=20.x

* doc

* doc

* lock

* fix: ts

* doc

* doc

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Co-authored-by: archer <archer@archerdeMac-mini.local>
Co-authored-by: archer <545436317@qq.com>