Migrate the PerpetuumServer to .net core or .net 8 for linux compatibility

[clouths]

The current Development branch is using .net v4.6.1
The goal is to migrate to either .net core 2+ or .net 8.
This will enable development on linux and also macos.

[PMZFX]

I’ve independently completed a native Linux port of the five headless server projects, targeting .NET 10. The work is isolated from our later gameplay/AI changes in two commits here:

https://github.com/PMZFX/PerpetuumServer/tree/perpetuum-ai/net10-port

It is based on the exact P31 commit (52ded128), rather than current Development. The Linux container builds successfully, initializes and connects to the P31 SQL Server database, loads all 59 enabled zones, reaches Online, and shuts down cleanly through SIGTERM.

I’ve also tested it with the stock Steam client through login, character selection, market purchase, undocking, zone authentication, movement, redocking, server restart, and reconnect with persisted state.

The WPF AdminTool and Windows Service host remain Windows-only; the Linux dependency graph covers the console/headless server. There are also a few non-startup System.Drawing.Common handlers still needing migration or explicit platform gating.

This branch is not yet rebased onto current Development, which is now 29 commits beyond the P31 base. If there is still maintainer interest, I’d be happy to discuss turning the isolated port into an upstreamable PR. Otherwise, the branch may at least serve as a working reference implementation for this issue.