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/ClientPatcher.cs

@@ -58,10 +58,11 @@ public sealed class ClientPatcher
         string photonVoiceAppId,
         string photonRegion,
         string apexHost,
+        bool singleOrigin = false,
         CancellationToken ct = default)
     {
         return Task.Run(() => ApplyCore(patcherDir, recRoomDataPath,
-            photonAppId, photonVoiceAppId, photonRegion, apexHost), ct);
+            photonAppId, photonVoiceAppId, photonRegion, apexHost, singleOrigin), ct);
     }
 
     private PatchResult ApplyCore(
@@ -70,7 +71,8 @@ public sealed class ClientPatcher
         string photonAppId,
         string photonVoiceAppId,
         string photonRegion,
-        string apexHost)
+        string apexHost,
+        bool singleOrigin)
     {
         var log = new System.Text.StringBuilder();
         try
@@ -217,7 +219,8 @@ public sealed class ClientPatcher
                     .Replace("{PHOTON_APPID}", photonAppId ?? "")
                     .Replace("{PHOTON_VOICE_APPID}",
                         string.IsNullOrEmpty(photonVoiceAppId) ? photonAppId ?? "" : photonVoiceAppId)
-                    .Replace("{PHOTON_REGION}", string.IsNullOrEmpty(photonRegion) ? "us" : photonRegion);
+                    .Replace("{PHOTON_REGION}", string.IsNullOrEmpty(photonRegion) ? "us" : photonRegion)
+                    .Replace("{SINGLE_ORIGIN_BASE_URL}", singleOrigin ? $"https://{apexHost}" : "");
                 File.WriteAllText(configDest, rendered);
                 log.AppendLine($"[patch] wrote config: {Path.GetFileName(configDest)}");
             }