- Updated `make-app-release` script to use `macdeployqt` with proper verbosity and bundle fixup.
- Introduced post-build fixup using CMake's `BundleUtilities` to internalize non-Qt dylibs.
- Enhanced macOS bundle RPATH settings for accurate Framework resolution.
- Added optional `kge_fixup_bundle` CMake target for post-build handling.
- Refined `default.nix` to load Nixpkgs in a default argument.
- Added `QtFrontend`, `QtRenderer`, and `QtInputHandler` for Qt-based UI rendering and input handling.
- Implemented support for theming, font customization, and palette overrides in GUITheme.
- Renamed and refactored ImGui-specific components (e.g., `GUIRenderer` -> `ImGuiRenderer`).
- Added cross-frontend integration for commands and visual font picker.
