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/ErrorTranslator.cs

@@ -61,7 +61,17 @@ public static class ErrorTranslator
 
     private static FriendlyError? TryMatch(Exception ex)
     {
-        // Network — GitHub releases, Tunnelto tunnel API, etc.
+        if (ex.Message.Contains("localtunnel", StringComparison.OrdinalIgnoreCase) ||
+            ex.Message.Contains("loca.lt", StringComparison.OrdinalIgnoreCase))
+        {
+            return new FriendlyError(
+                "Localtunnel couldn't get a URL.",
+                TrimToSentence(ex.Message) +
+                " Localtunnel sometimes rate-limits or blips. Retry in a minute, or switch hosting mode to LAN if your friends are local.",
+                "Retry");
+        }
+
+        // Network — GitHub releases, legacy tunnel APIs, etc.
         if (ex is HttpRequestException http)
         {
             return new FriendlyError(
@@ -80,6 +90,17 @@ public static class ErrorTranslator
                 "Retry");
         }
 
+        if (ex is TimeoutException timeout)
+        {
+            var title = timeout.Message.Contains("Tunnelto", StringComparison.OrdinalIgnoreCase)
+                ? "Tunnelto tunnel timed out."
+                : "Download timed out.";
+            return new FriendlyError(
+                title,
+                TrimToSentence(timeout.Message) + " Try again in a minute; if it repeats, Tunnelto or GitHub may be blocked on this network.",
+                "Retry");
+        }
+
         if (ex is SocketException sock)
         {
             return new FriendlyError(