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>

packages/core/test/settings.test.ts

@@ -1,11 +1,8 @@
 import { beforeEach, describe, expect, test } from "bun:test";
+
 import { clearAllTables, insertUser } from "@sofa/db/test-utils";
-import {
-  getSetting,
-  getUserCount,
-  isRegistrationOpen,
-  setSetting,
-} from "../src/settings";
+
+import { getSetting, getUserCount, isRegistrationOpen, setSetting } from "../src/settings";
 
 beforeEach(() => {
   clearAllTables();