Improve database dialog behavior and Linux packaging

[baldeuniversel]

Improve database dialog behavior and Linux packaging

• Enhanced database creation/registration dialog:
  • Option to create a directory when creating a new database
  • Auto-register the last accessed directory
  • Some security checks
• Embed ICU library in global package (for GNU/Linux portability)
• Remove embedded libc from opt/flamerobin/lib to prevent crashes on GNU/Linux
• Update GitHub Actions workflow file: .github/workflows/linux-build.yml
• Update Debian packaging files:
  • DEBIAN/*
  • deb/flamerobin/opt/flamerobin/bin/flamerobin-launcher
  • deb/flamerobin/opt/flamerobin/share/pixmaps/flamerobin.png

[baldeuniversel]

Update the workflows file -> [...linux-build.yml], now FlameRobin runs standalone on a fresh GNU/Linux system (Ubuntu 24.04) :

• All runtime dependencies (e.g. ICU, wxWidgets(deps), libfbclient) are bundled with appropriate RPATH using $ORIGIN
• Add binary/library stripping to reduce final package size

Update the file -> [...DEBIAN/control] :

• Remove unnecessary system-level dependencies

[mariuz]

/gemini review