build: Linux dedicated server preset + deploy package (systemd + install script)

- export_presets.cfg: ajout preset.1 Linux Server (dedicated_server=true, embed_pck=true, x86_64)
- builds/DauphinCraftServer.x86_64: binaire serveur Linux 76MB
- builds/run_server.sh: launcher avec port configurable
- deploy/: dauphincraft.service (systemd) + install.sh (VM setup)
- deploy_package/: tarball + scripts prêts à transférer sur VM
- Rebuild client Windows inclus (DauphinCraft.exe 100MB, exit 0)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

deploy/dauphincraft.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=DauphinCraft Dedicated Server
+After=network.target
+
+[Service]
+Type=simple
+User=dauphin
+Group=dauphin
+WorkingDirectory=/opt/dauphincraft
+ExecStart=/opt/dauphincraft/DauphinCraftServer.x86_64 --server --port 7777 --headless
+Restart=always
+RestartSec=5
+StandardOutput=append:/var/log/dauphincraft.log
+StandardError=append:/var/log/dauphincraft.log
+
+[Install]
+WantedBy=multi-user.target