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.

server/deploy/brass-sigil-server.service

@@ -0,0 +1,26 @@
+[Unit]
+Description=Brass & Sigil Minecraft server (with web admin panel)
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=matt
+Group=matt
+WorkingDirectory=/home/matt/brass-sigil-server
+ExecStart=/home/matt/brass-sigil-server/brass-sigil-server run
+Restart=on-failure
+RestartSec=10s
+
+# Give the JVM enough room to start up gracefully on Stop (sends "stop" to MC,
+# waits for clean shutdown, then escalates to SIGTERM/SIGKILL).
+TimeoutStopSec=60s
+KillMode=mixed
+
+# Tighten attack surface -- typical for a service running as a regular user.
+PrivateTmp=true
+ProtectSystem=full
+NoNewPrivileges=true
+
+[Install]
+WantedBy=multi-user.target