refactor: replace Biome with oxlint + oxfmt

Migrate the entire monorepo from Biome 2.4.7 to oxlint 1.56.0 (linter)
and oxfmt 0.41.0 (formatter) for faster lint/format and broader rule
coverage.

- Add `.oxlintrc.json` with React, TypeScript, unicorn, import plugins
  and correctness/suspicious categories
- Add `.oxfmtrc.json` with 2-space indent, import sorting, and Tailwind
  class sorting (all 30+ custom className attributes migrated)
- Add `docs/.oxlintrc.json` and `docs/.oxfmtrc.json` with Next.js plugin
- Update all 12 workspace package.json scripts: `oxlint`, `oxfmt`,
  `oxfmt --check`
- Add `format:check` turbo task and CI step
- Update VS Code settings/extensions to use `oxc.oxc-vscode`
- Update CI path triggers from `biome.json` to new config files
- Remove all `biome-ignore` comments and fix shadowed variables
- Delete `biome.json` and `docs/biome.json`
- Reformat entire codebase with oxfmt

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/README.md

@@ -1,7 +1,6 @@
 # sofa-docs
 
-This is a Next.js application generated with
-[Create Fumadocs](https://github.com/fuma-nama/fumadocs).
+This is a Next.js application generated with [Create Fumadocs](https://github.com/fuma-nama/fumadocs).
 
 Run development server:
 
@@ -36,10 +35,8 @@ Read the [Introduction](https://fumadocs.dev/docs/mdx) for further details.
 
 ## Learn More
 
-To learn more about Next.js and Fumadocs, take a look at the following
-resources:
+To learn more about Next.js and Fumadocs, take a look at the following resources:
 
-- [Next.js Documentation](https://nextjs.org/docs) - learn about Next.js
-  features and API.
+- [Next.js Documentation](https://nextjs.org/docs) - learn about Next.js features and API.
 - [Learn Next.js](https://nextjs.org/learn) - an interactive Next.js tutorial.
 - [Fumadocs](https://fumadocs.dev) - learn about Fumadocs