fix: encapsulate OpenGL types in VertexAttribute to eliminate raw GL API usage in tests

- Add VertexAttributeType and VertexAttributeNormalized enums in OpenGLVertexArray.h
- Add ToGLAttributeType() converter in OpenGLVertexArray.cpp
- Remove glActiveTexture() call from quad test (already handled by texture.Bind())
- Remove #include <glad/glad.h> from triangle test
- Update unit tests to use encapsulated enums

All three OpenGL integration tests (minimal, triangle, quad) pass with 0% pixel difference.

tests/RHI/OpenGL/unit/test_vertex_array.cpp

@@ -25,8 +25,8 @@ TEST_F(OpenGLTestFixture, VertexArray_AddVertexBuffer) {
     VertexAttribute attr;
     attr.index = 0;
     attr.count = 3;
-    attr.type = GL_FLOAT;
-    attr.normalized = false;
+    attr.type = VertexAttributeType::Float;
+    attr.normalized = VertexAttributeNormalized::False;
     attr.stride = sizeof(float) * 3;
     attr.offset = 0;
     
@@ -84,16 +84,16 @@ TEST_F(OpenGLTestFixture, VertexArray_Bind_MultipleAttributes) {
     VertexAttribute attrPos;
     attrPos.index = 0;
     attrPos.count = 2;
-    attrPos.type = GL_FLOAT;
-    attrPos.normalized = false;
+    attrPos.type = VertexAttributeType::Float;
+    attrPos.normalized = VertexAttributeNormalized::False;
     attrPos.stride = sizeof(float) * 2;
     attrPos.offset = 0;
     
     VertexAttribute attrColor;
     attrColor.index = 1;
     attrColor.count = 4;
-    attrColor.type = GL_FLOAT;
-    attrColor.normalized = false;
+    attrColor.type = VertexAttributeType::Float;
+    attrColor.normalized = VertexAttributeNormalized::False;
     attrColor.stride = sizeof(float) * 4;
     attrColor.offset = 0;