Increase baseline unit coverage for untested bean and file-upload paths

[Copilot]

This project had broad mixed functionality with minimal test coverage, leaving many simple core classes unverified. This PR adds focused unit tests across high-signal, low-dependency classes to materially improve baseline coverage and reduce regression risk.

• Coverage expansion in com.hazendaz.beans
  • Added tests for:
    • RandomHelper (genRand, rand, randomstring bounds/shape assertions)
    • InventoryVendorList (constructor state and getCount null/non-null branches)
    • PopupBean (duplicate toggle behavior and generic testExtends invocation)
    • ByteManipulation (main output behavior via captured System.out)
• Coverage expansion in com.hazendaz.fileupload
  • Added tests for:
    • UploadedImage (setData, setLength, and MIME selection in setName for csv/non-csv/no-extension inputs)
    • FileUploadBean (cancel flow, upload list clearing, date/files setters, size/null handling, timestamp/now format, no-op setNow, and paint stream-writing path)
• Behavioral focus
  • Tests target existing observable behavior and branch paths without changing production code contracts.

Example (new coverage around MIME branching in UploadedImage):

final UploadedImage image = new UploadedImage();

image.setName("data.csv");
Assertions.assertEquals("text/csv", image.getMime());

image.setName("data.txt");
Assertions.assertEquals("text/unknown", image.getMime());