Initial commit: Brass & Sigil monorepo

Self-hosted Minecraft modpack distribution + administration system.

- launcher/  Avalonia 12 desktop client; single-file win-x64 publish.
             Microsoft auth via XboxAuthNet, manifest+SHA-1 mod sync,
             portable install path, sidecar settings.
- server/    brass-sigil-server daemon (.NET 8, linux-x64). Wraps the
             MC subprocess, embedded Kestrel admin panel with cookie
             auth + rate limiting, RCON bridge, scheduled backups,
             BlueMap CLI integration with player markers + skin proxy,
             friend-side whitelist request flow, world wipe with seed
             selection (keep current / random / custom).
- pack/      pack.lock.json (Modrinth + manual CurseForge entries),
             data-only tweak source under tweaks/, build outputs in
             overrides/ (gitignored).
- scripts/   Build-Pack / Build-Tweaks / Update-Pack / Check-Updates
             plus Deploy-Brass.ps1 unified one-shot deploy with
             version-bump pre-flight and daemon-state detection.

launcher/Program.cs

@@ -0,0 +1,24 @@
+using Avalonia;
+using System;
+
+namespace ModpackLauncher;
+
+class Program
+{
+    // Initialization code. Don't use any Avalonia, third-party APIs or any
+    // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
+    // yet and stuff might break.
+    [STAThread]
+    public static void Main(string[] args) => BuildAvaloniaApp()
+        .StartWithClassicDesktopLifetime(args);
+
+    // Avalonia configuration, don't remove; also used by visual designer.
+    public static AppBuilder BuildAvaloniaApp()
+        => AppBuilder.Configure<App>()
+            .UsePlatformDetect()
+#if DEBUG
+            .WithDeveloperTools()
+#endif
+            .WithInterFont()
+            .LogToTrace();
+}