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/Findimplot.cmake

@@ -0,0 +1,52 @@
+# ==============================================================================
+# Find implot
+# ==============================================================================
+# Builds ImPlot from the bundled sources in deps/implot/.
+#
+# Targets provided:
+#   implot::implot - The ImPlot library target
+#
+# Variables set:
+#   implot_FOUND       - TRUE if implot is available
+#   implot_LIBRARIES   - The implot library target (implot::implot)
+#   implot_INCLUDE_DIR - Include directories for implot
+#
+# Configuration (set before find_package):
+#   IMPLOT_BUILD_DEMO - Include demo sources (default: ON)
+# ==============================================================================
+
+if (DEFINED _FINDIMPLOT_INCLUDED)
+    return()
+endif()
+set(_FINDIMPLOT_INCLUDED TRUE)
+
+option(IMPLOT_BUILD_DEMO "Include ImPlot demo sources" ON)
+
+set(_implot_source_dir "${CMAKE_CURRENT_LIST_DIR}/implot")
+
+if (NOT EXISTS "${_implot_source_dir}/implot.cpp")
+    message(FATAL_ERROR "implot sources not found at '${_implot_source_dir}'")
+endif()
+
+if (NOT TARGET imgui::imgui)
+    message(FATAL_ERROR "implot requires imgui::imgui to be available before find_package(implot)")
+endif()
+
+add_subdirectory("${_implot_source_dir}" "${CMAKE_BINARY_DIR}/_deps/implot-build" EXCLUDE_FROM_ALL)
+
+if (NOT TARGET implot::implot)
+    message(FATAL_ERROR "implot: target implot::implot was not created")
+endif()
+
+set(implot_FOUND      TRUE)
+set(implot_LIBRARIES  implot::implot)
+get_target_property(_implot_inc implot INTERFACE_INCLUDE_DIRECTORIES)
+set(implot_INCLUDE_DIR "${_implot_inc}")
+
+if (_implot_inc AND TARGET implot)
+    set_target_properties(implot PROPERTIES
+        INTERFACE_SYSTEM_INCLUDE_DIRECTORIES "${_implot_inc}"
+    )
+endif()
+
+set(IMPLOT_LICENSE_FILE "${_implot_source_dir}/LICENSE" CACHE FILEPATH "Path to ImPlot license file")