Summary

This PR adds Linux desktop support to BitFun, enabling builds for Debian/Ubuntu (.deb), RPM-based distros (.rpm), and universal AppImage packages.

Changes

• Build Scripts: Added 4 npm scripts for Linux builds:

  • `desktop:build:linux` - Full Linux build (all formats)
  • `desktop:build:linux:deb` - Debian package only
  • `desktop:build:linux:rpm` - RPM package only
  • `desktop:build:linux:appimage` - AppImage only

• Tauri Configuration: Updated `tauri.conf.json` with:

  • Linux bundle configuration
  • Added `icon.png` for Linux icon support
  • Debian package dependencies (libwebkit2gtk-4.1-0, libgtk-3-0)

• Documentation:

  • Updated README.md with Linux platform badge and build instructions
  • Created `docs/linux-setup.md` with system requirements for Debian/Ubuntu, Arch, and Fedora

Test Plan

• Install system dependencies per `docs/linux-setup.md`
• Run `pnpm run desktop:build:linux`
• Verify `.deb` package is created in `src/apps/desktop/target/release/bundle/`
• Install and test the generated package

Notes

• Debug build tested successfully (698MB binary)
• Release bundle build requires significant time (30+ minutes typical for Rust release builds)
• No changes to core application code - only build configuration and documentation