v1.0.1 — Fix: macOS app couldn't launch its browser

The downloadable macOS app failed at login with an "Internal server error".
Inside a frozen .app, Playwright resolved Chromium to a path inside the
read-only bundle and could neither install nor launch it, so every login died at
chromium.launch(). Fixed by pinning the browser cache (and the app's data dir)
to the standard writable per-OS locations.

Fixed

• Desktop app login on the packaged macOS build. chromium.launch() failed
  with Executable doesn't exist at …/BookVault.app/…/.local-browsers/… because
  a frozen Playwright defaults its browsers path relative to the (read-only)
  bundle. The launcher now sets PLAYWRIGHT_BROWSERS_PATH to the standard
  ~/Library/Caches/ms-playwright cache — writable, persistent, and shared with
  any normal Playwright install on the machine.

Changed

• The frozen entry point moved to a single cross-platform packaging/entry.py
  (per-user data dir + browsers path chosen by OS), shared by all packaged
  builds.