Add SDL3 GPU backend (Vulkan/Metal) with OpenGL fallback

CMakeLists.txt

@@ -17,6 +17,9 @@ set(OpenGL_GL_PREFERENCE GLVND)
 # --- LISTA EXPLÍCITA DE FUENTES ---
 set(APP_SOURCES
     src/main.cpp
+    src/rendering/shader_backend.cpp
+    src/rendering/opengl_shader_backend.cpp
+    src/rendering/sdl3gpu/sdl3gpu_shader_backend.cpp
 )
 
 # Fuentes de librerías de terceros
@@ -29,6 +32,21 @@ set(EXTERNAL_SOURCES
 find_package(SDL3 REQUIRED CONFIG REQUIRED COMPONENTS SDL3)
 message(STATUS "SDL3 encontrado: ${SDL3_INCLUDE_DIRS}")
 
+# --- COMPILACIÓN DE SHADERS (Vulkan SPIR-V) ---
+find_program(GLSLC_EXE NAMES glslc)
+if(GLSLC_EXE)
+    message(STATUS "glslc encontrado: ${GLSLC_EXE}")
+    add_custom_target(compile_shaders
+        COMMAND ${CMAKE_COMMAND}
+            -D GLSLC=${GLSLC_EXE}
+            -D SHADERS_DIR=${CMAKE_SOURCE_DIR}/shaders
+            -P ${CMAKE_SOURCE_DIR}/tools/shaders/compile_shaders.cmake
+        WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+        COMMENT "Compiling .vk.glsl shaders to SPIR-V")
+else()
+    message(STATUS "glslc no encontrado — el target compile_shaders no estará disponible")
+endif()
+
 # --- AÑADIR EJECUTABLE ---
 add_executable(${PROJECT_NAME} ${APP_SOURCES} ${EXTERNAL_SOURCES})