fix(cmake): afegir cmake/spv_to_header.cmake per convertir SPIR-V a headers C++

El fitxer era referenciat per CMakeLists.txt però mai no s'havia creat,
causant error de build immediat. Genera arrays uint8_t embeguts a partir
dels binaris .spv compilats per glslc.

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

cmake/spv_to_header.cmake

@@ -0,0 +1,20 @@
+# Converts a SPIR-V binary to a C++ header with an embedded uint8_t array.
+# cmake -DINPUT=<spv> -DOUTPUT=<h> -DVAR_NAME=<name> -P spv_to_header.cmake
+
+if(NOT DEFINED INPUT OR NOT DEFINED OUTPUT OR NOT DEFINED VAR_NAME)
+    message(FATAL_ERROR "Usage: -DINPUT=x.spv -DOUTPUT=x.h -DVAR_NAME=kname -P spv_to_header.cmake")
+endif()
+
+file(READ "${INPUT}" raw_hex HEX)
+string(REGEX REPLACE "([0-9a-fA-F][0-9a-fA-F])" "0x\\1," hex_bytes "${raw_hex}")
+string(REGEX REPLACE ",$" "" hex_bytes "${hex_bytes}")
+string(LENGTH "${raw_hex}" hex_len)
+math(EXPR byte_count "${hex_len} / 2")
+
+file(WRITE "${OUTPUT}"
+"#pragma once
+#include <cstdint>
+#include <cstddef>
+static const uint8_t ${VAR_NAME}[] = { ${hex_bytes} };
+static const size_t ${VAR_NAME}_size = ${byte_count};
+")