Remove generated changelog.gz from version control

The debian/usr/share/doc/skyview-adsb/changelog.gz file is automatically
generated during the Debian package build process and should not be
tracked in version control. It's created fresh from git history each
time the package is built.

- Removed changelog.gz from git tracking
- Added to .gitignore to prevent re-addition
- Ensures clean builds without git conflicts

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

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

.gitignore

@@ -6,6 +6,7 @@ dist/
 # Debian package build artifacts
 debian/usr/bin/skyview
 debian/usr/bin/beast-dump
+debian/usr/share/doc/skyview-adsb/changelog.gz
 
 # Configuration
 config.json