Fix unicorn filename-case linting for Vue files

What does this MR do and why?

Closes #549 (closed).

After eslint-plugin-unicorn v65, unicorn/filename-case checks directory names in addition to filenames. This breaks linting for Vue files under the conventional Rails/Vite app/javascript directory, because app is not PascalCase.

This MR disables directory-name checks for the Vue filename-case rule while preserving PascalCase enforcement for .vue filenames.

I intentionally used checkDirectories: false instead of ignore: [/^app$/], because ignore would ignore matching path segments and skip the rule for files under app, which would not preserve filename PascalCase enforcement.

Screenshots or screen recordings

Before	After

Validation steps

cd contributors
npm ci
npm run lint

/cc @leetickett-gitlab @aharadon

Closes #549 (closed)