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/graph_renderer.h

@@ -0,0 +1,28 @@
+#pragma once
+#include <cstdint>
+
+struct GraphData; // forward declare
+
+struct GraphRendererConfig {
+    float node_outline     = 1.5f;   // outline width in pixels
+    float edge_width       = 1.0f;   // edge line width
+    float edge_alpha       = 0.4f;   // edge transparency
+    uint32_t bg_color      = 0xFF1A1A1E; // ABGR background
+    bool edge_fade_alpha   = true;   // fade edge alpha by distance to camera
+    // Default palette for communities (when node.color == 0)
+    // 10 distinct colors, ABGR packed
+};
+
+struct GraphRenderer;
+
+// Lifecycle
+GraphRenderer* graph_renderer_create(int width, int height, const GraphRendererConfig& config = {});
+void graph_renderer_destroy(GraphRenderer* r);
+void graph_renderer_resize(GraphRenderer* r, int width, int height);
+
+// Render graph to internal FBO.
+// cam_x, cam_y: camera center in graph space
+// cam_zoom: zoom level (1.0 = 1:1 pixel mapping)
+// Returns OpenGL texture ID suitable for ImGui::Image().
+unsigned int graph_renderer_draw(GraphRenderer* r, const GraphData& graph,
+                                  float cam_x, float cam_y, float cam_zoom);