Localtunnel hosting + admin panel + AppData db

- Default hosting mode is now Localtunnel — public *.loca.lt URL,
  no account, auto-fetched on first run. Replaces the prototyped
  Tailscale mode.
- Tailscale code purged from launcher + CLI; docs swapped to
  Localtunnel throughout (easy-setup, joining-a-server, server-cli,
  troubleshooting, faq, READMEs).
- Launcher sidebar gains an Open admin panel button — opens
  https://admin.<apex> in the browser once the server is live.
- SQLite db moves to %APPDATA%\DorkNet\dorknet.db (server reads
  Database__SqlitePath env var, launcher passes it). Existing dbs
  under <serverDir>\data\ are migrated on first run.
- CLI Program.cs: --mode default flips from tailscale to localtunnel;
  csproj links in LocaltunnelTunnel + LocaltunnelInstaller.
- New Backend files: LauncherNameServer, LocaltunnelInstaller,
  LocaltunnelTunnel, SingleOriginServiceMap.
- .gitignore: exclude installer/out/.

launcher/Backend/LocalNetwork.cs

@@ -5,15 +5,15 @@ using System.Net.Sockets;
 namespace DorkNet.Launcher.Backend;
 
 /// <summary>Finds the machine's preferred LAN IPv4 address for
-/// "local network" hosting mode. Skip Cloudflare entirely, hand
+/// "local network" hosting mode. Skip public tunnels entirely, hand
 /// out an sslip.io hostname derived from the LAN IP in the join code,
 /// and players on the same network connect direct.
 ///
 /// <para>Selection priority: an "Up" non-loopback network interface
 /// with a private (RFC1918) IPv4 address. Falls back to 127.0.0.1
 /// if nothing usable is found — works for solo testing on one
-/// machine but joiners need either a real LAN address or
-/// Cloudflare mode.</para></summary>
+/// machine but joiners need either a real LAN address or one of the
+/// tunnel modes (Localtunnel / Tunnelto).</para></summary>
 public static class LocalNetwork
 {
     private const string SslipDomain = "sslip.io";