Fix macOS GUI build to bundle customtkinter and show proper installer title

🤔 Why?

• The macOS package produced by CI missed GUI runtime dependencies (notably customtkinter), causing the app to crash on startup with ModuleNotFoundError.
• The macOS Installer window also lacked a friendly product title, making the installed app appear less polished.

🔧 What changed

• Ensure GUI runtime deps (customtkinter, Pillow) are installed into the uvx Python used in CI so PyInstaller can analyze and bundle them.
• Add a PyInstaller hook (pyinstaller-hooks/hook-customtkinter.py) to reliably collect customtkinter submodules and data files.
• Update the macOS packaging step to pass a human-friendly installer title to productbuild so the Installer GUI shows "MkPFS ".

🧪 How to test

• Run the CI mac build or the mac packaging steps locally.

• Install the produced .pkg and then run:

  /Applications/MkPFS.app/Contents/MacOS/MkPFS

  Confirm the GUI launches without ModuleNotFoundError and that the Installer window displays the product title/version.

💬 Notes for non-technical readers

• This fixes crashes on macOS caused by a missing GUI dependency and makes the installer display a proper product name. The application code and user data are unchanged.