Add ZIP bulk upload to asset manager

Features:
- Upload ZIP files with folder structure
- Automatic extraction and MD5/SHA256 calculation
- Preserve folder paths as EA CDN paths
- Auto-categorize based on file extensions
- Update existing assets automatically
- Bootstrap tabs for single/bulk upload UI
- Progress feedback (X new, Y updated)

Example: cars/porsche.dat → /cars/porsche.dat

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

RR3CommunityServer/obj/Debug/net8.0/RR3CommunityServer.AssemblyInfoInputs.cache

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+57cc4aab962a2ad12c842505535b2be3f034220ea319669b999c8dc52168130d