feat: add multi-viewport support and SQLite amalgamation to C++ framework

- AppConfig.viewports flag para ventanas OS reales fuera del main window
- Multi-viewport render loop en app_base.cpp (UpdatePlatformWindows)
- SQLite amalgamation vendoreada para Windows cross-compile
- LANGUAGES C CXX en CMakeLists para compilar sqlite3.c
- Fix pie_chart.cpp para nueva API de ImPlot (PlotPieChart sin flags arg)
- imgui.ini añadido a gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -54,3 +54,4 @@ Thumbs.db
 .local
 
 broken_paths.txt
+imgui.ini