Fix(#119): deleteFolder should use fs.rm to remove directories

[everleepham]

Summary

Fix the deleteFolder helper in src/controller/package.ts to use fs.rm() with { recursive: true, force: true } instead of fs.unlink(). fs.unlink is a unlink syscall and can only remove files so when it is called on a directory it fails with EISDIR on Linux/macOS or EPERM on Windows, leaving orphaned application directories on disk after failed uploads.

Related issue

Fixes #119

Type of change

• Bug fix

How to test

1. Checkout the branch
2. Run npm ci
3. Run npm test -> all 16 tests should pass, including 2 new tests in the Fix: deleteFolder should use fs.rm to remove directories

Checklist

• I have read the contributing guidelines
• I added tests that prove my fix is effective or that my feature works

Notes for reviewers

• The callback-style fs.rm(path, { recursive, force }, cb) is available since Node 14.14, this project requires Node ≥18.17, so it's safe.
• The same fs.rm pattern is already used in src/index.ts and src/controller/repository.ts
• deleteBlob (line 155) correctly uses fs.unlink since it removes a single file, no need to change.