Add support for 7z compression

Objo now includes first-class .7z archive support through a new SevenZip standard-library family. Apps can create archives from folders, extract archives safely, validate archives, inspect entries, and build ordered archives with SevenZipWriter.

The implementation is backed by managed SharpCompress and is bundled into Objo Studio's build/publish pipeline, so Studio-built apps remain self-contained single-file publishes and users do not need 7-Zip, 7z.dll, or other external archive dependencies installed.

SevenZip creation supports LZMA and LZMA2 compression, compressed headers, overwrite options, and base-folder inclusion. Reading and extraction support password-protected archives. Extraction rejects unsafe archive entries such as absolute paths, drive-qualified paths, traversal segments, links, split/incomplete entries, anti-items, and unsupported entries.