Fry3DX 0.5: builds for Windows, Linux and Android, a phone layout, Apache 2.0

- Apache License 2.0
- Windows: cross-built with clang-cl (cmake --preset windows), a window
  program with its icon; Linux: a portable preset (SDL and the C++
  library inside); Android: android/build_apk.py makes the APK
- tools/package.py packs the downloads; a GitHub workflow builds all
  three and makes a release for a v* tag
- A phone layout (fry_touch, on by default on Android): the UI drawn
  bigger, panels when asked for, a bar of big buttons, one finger to
  turn the view, two to move and pinch, a long press for a right-click;
  files through the phone's file picker
- Settings and autosaves now in a Nexoniarz folder (copied over once)
- README rewritten, the website shows the downloads and the phone

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NMSrd5oe1GpUD7E6d825KP

engine/rhi/gl/gl_backend.cpp

@@ -9,6 +9,7 @@
 //     window-space winding, so front faces are clockwise. Only the final blit to the window
 //     (which shows row 0 at the bottom) flips.
 // Requires ARB_bindless_texture (NVIDIA, AMD); without it init fails and the engine uses Vulkan.
+#include "ui/ui.h"
 #include "render/backend.h"
 #include "render/screenshot.h"
 #include "rhi/gl/gl_loader.h"
@@ -332,6 +333,7 @@ public:
     void beginUi() override {
         ImGui_ImplOpenGL3_NewFrame();
         ImGui_ImplSDL3_NewFrame();
+        ui::applyPixelScale();
         ImGui::NewFrame();
     }
     void setVsync(bool on) override { SDL_GL_SetSwapInterval(on ? 1 : 0); }

engine/rhi/gl/gl_legacy.cpp

@@ -6,6 +6,7 @@
 //   3.1  lightmaps, sun with shadows (one tap), sky, fog; flat surfaces, no highlights or lights
 // Neither has clustered lights, light shadows or occlusion culling. Depth is GL's -1..1 here
 // (no glClipControl), so vertex shaders turn the 0..1 matrices' z into it.
+#include "ui/ui.h"
 #include "render/backend.h"
 #include "core/log.h"
 #include "platform/window.h"
@@ -480,6 +481,7 @@ public:
     void beginUi() override {
         ImGui_ImplOpenGL3_NewFrame();
         ImGui_ImplSDL3_NewFrame();
+        ui::applyPixelScale();
         ImGui::NewFrame();
     }
     void setVsync(bool on) override { SDL_GL_SetSwapInterval(on ? 1 : 0); }