fix(installer): stamp Hermes icon onto Hermes.exe via rcedit (no winCodeSign)

The unpacked Hermes.exe showed the stock Electron icon + name in the
taskbar because build.win.signAndEditExecutable=false disables BOTH
electron-builder's signing AND its rcedit metadata/icon stamping. That
flag is load-bearing: enabling it re-triggers signtool -> winCodeSign,
whose macOS symlinks crash 7-Zip on non-admin Windows (unfixable dead end).

Decouple identity-stamping from signing entirely: after npm run pack,
run rcedit ourselves on the produced exe.
- Add rcedit as a direct devDependency of apps/desktop (the transitive
  electron-winstaller copy is fragile).
- apps/desktop/scripts/set-exe-identity.cjs: Node helper that calls
  rcedit's named export to set icon + ProductName/FileDescription/
  CompanyName. Node builds argv natively — avoids the PowerShell->exe
  ->JSON double-escaping that broke the app-builder rcedit path.
- install.ps1 Set-DesktopExeIdentity invokes the script after the build,
  before shortcuts. Best-effort: failure keeps the stock icon, never
  fails the install. rcedit is a pure PE editor — no signtool, no
  winCodeSign, no symlinks.

Verified locally: stamping a copy of the built Hermes.exe embeds the
32x32 icon and sets ProductName=Hermes.

Also fix update-path success-screen flash: in update mode the installer
hands off + exits in ~600ms, so don't route to the 'launch Hermes'
success view (it flashed before the window closed).

apps/desktop/package.json

@@ -116,6 +116,7 @@
     "globals": "^16.5.0",
     "jsdom": "^29.1.1",
     "prettier": "^3.8.3",
+    "rcedit": "^5.0.2",
     "typescript": "^6.0.3",
     "vite": "^8.0.10",
     "vitest": "^4.1.5",