build(deps-dev): Bump vitest from 4.1.8 to 4.1.9

Bumps [vitest](https://github.com/vitest-dev/vitest/tree/HEAD/packages/vitest) from 4.1.8 to 4.1.9.
- [Release notes](https://github.com/vitest-dev/vitest/releases)
- [Changelog](https://github.com/vitest-dev/vitest/blob/main/docs/releases.md)
- [Commits](https://github.com/vitest-dev/vitest/commits/v4.1.9/packages/vitest)

---
updated-dependencies:
- dependency-name: vitest
  dependency-version: 4.1.9
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package-lock.json

@@ -33,7 +33,7 @@
     "typescript": "~6.0.3",
     "typescript-eslint": "^8.60.1",
     "vite": "^8.0.16",
-    "vitest": "^4.1.8"
+    "vitest": "^4.1.9"
   },
   "description": "A browser app for previewing GitHub Copilot usage-based billing reports.",
   "license": "MIT",