Check for updates silently on app launch

Adds a background update check 2 seconds after app launch using Sparkle's
checkForUpdatesInBackground(). Only shows UI if an update is available.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Merge branch 'main' of https://github.com/zmh/Quill

Add preview=true parameter to WordPress preview URL

Ensures unpublished/draft posts display correctly when previewing.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Fix pip install on macOS GitHub runner

Add --break-system-packages flag for Homebrew Python.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Enable Sparkle EdDSA signing for updates

Sign DMG with EdDSA private key and include signature in appcast.xml
to allow Sparkle to verify update authenticity.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Update About view and README download links

- Settings > About now shows dynamic version from bundle
- Added "A side project by Zachary Hamed" with link to zmh.org
- README download links now always point to latest release
- Workflow uploads stable Quill.dmg alongside versioned DMG

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Add author credit to About menu

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Add author credit to About menu

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Temporarily disable EdDSA signing to test Apple code signing

The Sparkle sign_update tool setup is complex. Disabling it temporarily
so we can first confirm that Apple Developer ID code signing works properly
and the DMG installs without Gatekeeper warnings.

EdDSA signing will be re-enabled once basic flow is confirmed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Temporarily disable EdDSA signing to test Apple code signing

The Sparkle sign_update tool setup is complex. Disabling it temporarily
so we can first confirm that Apple Developer ID code signing works properly
and the DMG installs without Gatekeeper warnings.

EdDSA signing will be re-enabled once basic flow is confirmed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>