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/candlestick.cpp

@@ -0,0 +1,81 @@
+#include "viz/candlestick.h"
+#include "imgui.h"
+#include "implot.h"
+
+void candlestick(const char* title, const double* dates, const double* opens,
+                 const double* closes, const double* lows, const double* highs,
+                 int count, float width_percent, bool tooltip) {
+    if (count <= 0) return;
+
+    // Compute half-width of each candle body in data coordinates.
+    // Use spacing between consecutive dates when count > 1, else fallback to 0.5.
+    double spacing = (count > 1) ? (dates[1] - dates[0]) : 1.0;
+    double half_w  = spacing * (double)width_percent * 0.5;
+
+    ImPlot::SetupAxes("Date", "Price", ImPlotAxisFlags_None, ImPlotAxisFlags_AutoFit);
+    ImPlot::SetupAxisScale(ImAxis_X1, ImPlotScale_Time);
+
+    // Auto-fit X axis to the data range with a small margin.
+    ImPlot::SetupAxisLimits(ImAxis_X1,
+                            dates[0]         - spacing,
+                            dates[count - 1] + spacing,
+                            ImGuiCond_Always);
+
+    if (ImPlot::BeginPlot(title, ImVec2(-1, 0))) {
+        ImDrawList* draw = ImPlot::GetPlotDrawList();
+
+        const ImU32 col_bull = IM_COL32(0,  200, 80,  255);  // green — close >= open
+        const ImU32 col_bear = IM_COL32(220, 50, 50,  255);  // red   — close < open
+
+        int hovered_idx = -1;
+
+        for (int i = 0; i < count; i++) {
+            double x     = dates[i];
+            double open  = opens[i];
+            double close = closes[i];
+            double low   = lows[i];
+            double high  = highs[i];
+
+            bool bullish = (close >= open);
+            ImU32 col   = bullish ? col_bull : col_bear;
+
+            // Convert data coordinates to screen pixels.
+            ImVec2 body_tl = ImPlot::PlotToPixels(x - half_w, bullish ? close : open);
+            ImVec2 body_br = ImPlot::PlotToPixels(x + half_w, bullish ? open  : close);
+            ImVec2 wick_hi = ImPlot::PlotToPixels(x, high);
+            ImVec2 wick_lo = ImPlot::PlotToPixels(x, low);
+            float  cx      = (body_tl.x + body_br.x) * 0.5f;
+
+            // Wick (high-low vertical line).
+            draw->AddLine(ImVec2(cx, wick_hi.y), ImVec2(cx, wick_lo.y), col, 1.5f);
+
+            // Body rectangle (open-close).
+            // Ensure at least 1px height so flat candles are visible.
+            if (body_br.y <= body_tl.y + 1.0f) body_br.y = body_tl.y + 1.0f;
+            draw->AddRectFilled(body_tl, body_br, col);
+            draw->AddRect(body_tl, body_br, col);
+
+            // Track hovered candle for tooltip.
+            if (tooltip && ImPlot::IsPlotHovered()) {
+                ImVec2 mouse = ImGui::GetMousePos();
+                if (mouse.x >= body_tl.x - 4 && mouse.x <= body_br.x + 4 &&
+                    mouse.y >= wick_hi.y  - 4 && mouse.y <= wick_lo.y  + 4) {
+                    hovered_idx = i;
+                }
+            }
+        }
+
+        // Tooltip for the hovered candle.
+        if (tooltip && hovered_idx >= 0) {
+            int i = hovered_idx;
+            ImGui::BeginTooltip();
+            ImGui::Text("O: %.4f", opens[i]);
+            ImGui::Text("H: %.4f", highs[i]);
+            ImGui::Text("L: %.4f", lows[i]);
+            ImGui::Text("C: %.4f", closes[i]);
+            ImGui::EndTooltip();
+        }
+
+        ImPlot::EndPlot();
+    }
+}