launcher: auto-strip SteamStub DRM before patching

Steam-purchased Rec Room ships with SteamStub Variant 3.1 wrapping
Recroom_Release.exe so it refuses to launch without Steam loaded.
DorkNet spawns the exe directly, so for Steam installs we have to
unwrap it first or the user gets a silent crash on Launch.

- SteamDrmStripper.StripIfNeededAsync: PE-walks the exe's section
  table looking for the .bind section SteamStub adds, and only
  invokes Steamless when that section is present. Re-runs detect
  the already-unwrapped exe and short-circuit. Backs up the
  original next to the exe as Recroom_Release.exe.steamwrapped.
- SteamlessInstaller: resolves a usable Steamless.CLI.exe via
  side-by-side -> %LOCALAPPDATA%\DorkNet\Steamless\ cache ->
  download v3.1.0.5 from atom0s/Steamless GitHub releases. Same
  pattern as CloudflaredInstaller.
- Inserted as a step between "Download client patcher" and "Patch
  your Rec Room install" in both host (5 -> 6 steps) and join
  (2 -> 3 steps). Step detail reports Stripped / AlreadyUnpacked /
  NotApplicable so the user sees what happened.

Oculus / Quest builds and already-unwrapped installs skip the
Steamless download entirely.

launcher/Backend/StartupStep.cs

@@ -78,12 +78,14 @@ public static class StartupFlow
         new StartupStep(isLocalNetwork ? "Find your local network address" : "Set up Cloudflare tunnel"),
         new StartupStep("Start the server"),
         new StartupStep("Download client patcher"),
+        new StartupStep("Unlock Rec Room from Steam (if needed)"),
         new StartupStep("Patch your Rec Room install"),
     };
 
     public static ObservableCollection<StartupStep> NewJoinFlow() => new()
     {
         new StartupStep("Download client patcher"),
+        new StartupStep("Unlock Rec Room from Steam (if needed)"),
         new StartupStep("Patch your Rec Room install"),
     };
 }