feat: add OpenGL abstraction layer with RAII resources

- Replace window class with cbt::opengl::context
- Add buffer resource (VBO, EBO, UBO, SSBO) with move semantics
- Add texture resource with format/type enums and filtering
- Add descriptor_set for Vulkan-style resource binding
- All resources use RAII with proper cleanup

deps/Findimnodes.cmake

@@ -0,0 +1,47 @@
+# ==============================================================================
+# Find imnodes
+# ==============================================================================
+# Builds imnodes from the bundled sources in deps/imnodes/.
+#
+# Targets provided:
+#   imnodes::imnodes - The imnodes library target
+#
+# Variables set:
+#   imnodes_FOUND       - TRUE if imnodes is available
+#   imnodes_LIBRARIES   - The imnodes library target (imnodes::imnodes)
+#   imnodes_INCLUDE_DIR - Include directories for imnodes
+# ==============================================================================
+
+if (DEFINED _FINDIMNODES_INCLUDED)
+    return()
+endif()
+set(_FINDIMNODES_INCLUDED TRUE)
+
+set(_imnodes_source_dir "${CMAKE_CURRENT_LIST_DIR}/imnodes")
+
+if (NOT EXISTS "${_imnodes_source_dir}/imnodes.cpp")
+    message(FATAL_ERROR "imnodes sources not found at '${_imnodes_source_dir}'")
+endif()
+
+if (NOT TARGET imgui::imgui)
+    message(FATAL_ERROR "imnodes requires imgui::imgui to be available before find_package(imnodes)")
+endif()
+
+add_subdirectory("${_imnodes_source_dir}" "${CMAKE_BINARY_DIR}/_deps/imnodes-build" EXCLUDE_FROM_ALL)
+
+if (NOT TARGET imnodes::imnodes)
+    message(FATAL_ERROR "imnodes: target imnodes::imnodes was not created")
+endif()
+
+set(imnodes_FOUND      TRUE)
+set(imnodes_LIBRARIES  imnodes::imnodes)
+get_target_property(_imnodes_inc imnodes INTERFACE_INCLUDE_DIRECTORIES)
+set(imnodes_INCLUDE_DIR "${_imnodes_inc}")
+
+if (_imnodes_inc AND TARGET imnodes)
+    set_target_properties(imnodes PROPERTIES
+        INTERFACE_SYSTEM_INCLUDE_DIRECTORIES "${_imnodes_inc}"
+    )
+endif()
+
+set(IMNODES_LICENSE_FILE "${_imnodes_source_dir}/LICENSE.md" CACHE FILEPATH "Path to imnodes license file")