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/.

docs/photon-setup.md

@@ -41,15 +41,15 @@ card.
 After login, click **CREATE A NEW APP** on the dashboard. The form asks
 for:
 
-- **Photon Type** — pick **Photon Realtime**. Not Fusion, not Quantum,
-  not Bolt.
+- **Photon Type** — pick **Photon SDK**. Not Fusion, not Quantum, not
+  Bolt.
 - **Name** — anything you'll recognise later ("DorkNet Realtime",
   "Sunday Server", etc.). Joiners don't see this.
 - **Description** — optional.
 
 Click **CREATE**.
 
-![photon "Create a new app" form, Realtime selected](images/photon-2-create-realtime.png)
+![photon "Create a new app" form, Photon SDK selected](images/photon-2-create-realtime.png)
 
 ## Step 3 — Copy the Realtime AppId