Add .gitignore and stop tracking build artifacts

Untrack the generated build/ directory and ignore CMake/CPack output,
Qt MOC/RCC artifacts, compiled binaries, and editor files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,56 @@
+# Build-Verzeichnisse
+/build/
+build*/
+cmake-build-*/
+out/
+
+# CMake-Artefakte
+CMakeCache.txt
+CMakeFiles/
+cmake_install.cmake
+CTestTestfile.cmake
+CPackConfig.cmake
+CPackSourceConfig.cmake
+install_manifest.txt
+_deps/
+Testing/
+
+# CPack-Pakete
+*.exe
+*.msi
+*.dmg
+*.deb
+*.rpm
+*-win64/
+_CPack_Packages/
+
+# Qt / MOC / RCC / UIC generiert
+moc_*.cpp
+moc_*.h
+qrc_*.cpp
+ui_*.h
+*.moc
+*_autogen/
+
+# Kompilate
+*.o
+*.obj
+*.so
+*.so.*
+*.a
+*.dll
+*.dylib
+*.exe
+
+# Editor / IDE
+.vscode/
+.idea/
+*.user
+*.swp
+*~
+.cache/
+compile_commands.json
+
+# OS
+.DS_Store
+Thumbs.db