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/.oxfmtrc.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "./node_modules/oxfmt/configuration_schema.json",
+  "proseWrap": "never",
+  "sortImports": {
+    "groups": ["builtin", "external", "internal", "parent", "sibling", "index"],
+    "internalPattern": ["@/", "@sofa/", "collections/"],
+    "newlinesBetween": true,
+    "order": "asc"
+  },
+  "sortTailwindcss": {
+    "attributes": ["classList"],
+    "functions": ["cn", "clsx", "cva"]
+  },
+  "ignorePatterns": [
+    "node_modules",
+    ".next",
+    "dist",
+    "build",
+    ".source",
+    "public/openapi.json",
+    "content/docs/api/**/*.mdx"
+  ]
+}