Add Homebrew Cask distribution for macOS

## Problem
Currently, macOS users need to manually download the DMG and run `xattr -cr /Applications/Thoth.app` to remove the quarantine attribute before they can use the app. This creates friction in the installation process.

## Solution
Set up Homebrew Cask distribution to provide a better installation experience for macOS users.

### Benefits:
- Users can install with `brew install --cask thoth`
- Homebrew handles quarantine removal automatically
- Easier updates via `brew upgrade`
- Better UX for technical macOS users
- No Apple Developer Program required

### Implementation Steps:
1. Create a Homebrew tap repository (e.g., `anitnilay20/homebrew-tap`)
2. Add a Cask formula that points to GitHub releases
3. Configure the formula to:
- Download the DMG from latest release
- Install to /Applications
- Handle quarantine attributes
4. Update README with Homebrew installation instructions
5. Optionally: Update release workflow to automatically update the Cask formula

### References:
- [Homebrew Cask Documentation](https://docs.brew.sh/Cask-Cookbook)
- Example casks from other Rust GUI apps

### Alternative:
Could also submit to the main homebrew-cask repository once the project is more mature.