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.cpp

@@ -0,0 +1,18 @@
+#include "viz/histogram.h"
+#include "implot.h"
+
+void histogram(const char* title, const float* values, int count, int bins) {
+    if (ImPlot::BeginPlot(title, ImVec2(-1, 0))) {
+        int b = (bins > 0) ? bins : ImPlotBin_Sturges;
+        ImPlot::PlotHistogram("##data", values, count, b);
+        ImPlot::EndPlot();
+    }
+}
+
+void histogram(const char* title, const double* values, int count, int bins) {
+    if (ImPlot::BeginPlot(title, ImVec2(-1, 0))) {
+        int b = (bins > 0) ? bins : ImPlotBin_Sturges;
+        ImPlot::PlotHistogram("##data", values, count, b);
+        ImPlot::EndPlot();
+    }
+}