feat: add C++ ImGui functions for core UI and visualization

Funciones C++/ImGui para dashboards (grid, panel, docking, sidebar, tabs),
visualizaciones (candlestick, gauge, histogram, pie, sparkline, heatmap,
scatter, line, bar, surface3d, kpi, table), grafos (force layout, renderer,
viewport, spatial hash, types) y utilidades (time series buffer, tracy zones,
memory/fps overlay, plot theme).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cpp/functions/viz/histogram.h

@@ -0,0 +1,7 @@
+#pragma once
+
+// Renders a histogram using ImPlot::PlotHistogram.
+// Call within an ImGui frame.
+// bins == -1: automatic bin count via Sturges' rule.
+void histogram(const char* title, const float* values, int count, int bins = -1);
+void histogram(const char* title, const double* values, int count, int bins = -1);