phase 2-6: complete D3/TopoJSON migration

Replace ZingChart + jQuery with D3 v7 + TopoJSON. Implements all
planned phases: choropleth map (NaturalEarth1 projection, YlOrRd
gradient), hover tooltip, zoom/pan/reset, country detail modal,
side-by-side compare, metric selector, label toggle, donut pie chart
with per-country drilldown bar chart. Upgrades Bootstrap JS bundle
from v4.5.3 (jQuery-dependent) to v5.0.0, fixes modal API calls
to use getInstance/constructor pattern compatible with BS 5.0.0+.
Removes jquery, zingchart ×3 library files.

2 files changed, 168 insertions, 4 deletions

diff --git a/assets/js/charts/bar.js b/assets/js/charts/bar.js
index 4aa61ef..572cb50 100644
--- a/assets/js/charts/bar.js
+++ b/assets/js/charts/bar.js
@@ -1,2 +1,97 @@
-// Phase 4: horizontal bar chart for top-N countries
-export function renderBarChart(container, data) {}
+import * as d3 from "https://cdn.jsdelivr.net/npm/d3@7/+esm";
+
+const MARGIN = { top: 44, right: 90, bottom: 30, left: 150 };
+
+// data: [{label, value (0–100 normalized), displayValue}]
+// opts: { title?, onBack? }
+export function renderBarChart(container, data, opts = {}) {
+	const { title, onBack } = opts;
+	const el = typeof container === "string"
+		? document.querySelector(container)
+		: container;
+
+	el.innerHTML = "";
+
+	const totalWidth = Math.max(el.clientWidth || 500, 400);
+	const totalHeight = data.length * 52 + MARGIN.top + MARGIN.bottom;
+	const width = totalWidth - MARGIN.left - MARGIN.right;
+	const height = totalHeight - MARGIN.top - MARGIN.bottom;
+
+	const svg = d3.select(el).append("svg")
+		.attr("width", "100%")
+		.attr("viewBox", `0 0 ${totalWidth} ${totalHeight}`);
+
+	if (title) {
+		svg.append("text")
+			.attr("x", totalWidth / 2)
+			.attr("y", 22)
+			.attr("text-anchor", "middle")
+			.style("fill", "#fff")
+			.style("font-size", "14px")
+			.style("font-weight", "bold")
+			.text(title);
+	}
+
+	if (onBack) {
+		svg.append("text")
+			.attr("x", 8)
+			.attr("y", 22)
+			.style("fill", "#24ab48")
+			.style("font-size", "13px")
+			.style("cursor", "pointer")
+			.text("← Back")
+			.on("click", onBack);
+	}
+
+	const g = svg.append("g")
+		.attr("transform", `translate(${MARGIN.left},${MARGIN.top})`);
+
+	const yScale = d3.scaleBand()
+		.domain(data.map(d => d.label))
+		.range([0, height])
+		.padding(0.3);
+
+	const xScale = d3.scaleLinear()
+		.domain([0, 100])
+		.range([0, width]);
+
+	// Y axis (country/metric labels)
+	g.append("g")
+		.call(d3.axisLeft(yScale).tickSize(0))
+		.call(ax => ax.select(".domain").remove())
+		.selectAll("text")
+		.style("fill", "#ccc")
+		.style("font-size", "12px");
+
+	// X axis (percentage)
+	g.append("g")
+		.attr("transform", `translate(0,${height})`)
+		.call(d3.axisBottom(xScale).ticks(5).tickFormat(d => d + "%"))
+		.call(ax => ax.select(".domain").remove())
+		.selectAll("text")
+		.style("fill", "#666")
+		.style("font-size", "10px");
+
+	// Bars
+	g.selectAll(".bar")
+		.data(data)
+		.join("rect")
+		.attr("class", "bar")
+		.attr("y", d => yScale(d.label))
+		.attr("height", yScale.bandwidth())
+		.attr("x", 0)
+		.attr("width", d => xScale(Math.max(0, d.value)))
+		.attr("fill", "rgba(36, 171, 72, 0.8)");
+
+	// Value labels at end of bar
+	g.selectAll(".bar-label")
+		.data(data)
+		.join("text")
+		.attr("class", "bar-label")
+		.attr("x", d => xScale(Math.max(0, d.value)) + 4)
+		.attr("y", d => yScale(d.label) + yScale.bandwidth() / 2)
+		.attr("dy", "0.35em")
+		.style("fill", "#fff")
+		.style("font-size", "11px")
+		.text(d => d.displayValue);
+}
diff --git a/assets/js/charts/pie.js b/assets/js/charts/pie.js
index ff5a2e5..d59f31a 100644
--- a/assets/js/charts/pie.js
+++ b/assets/js/charts/pie.js
@@ -1,2 +1,71 @@
-// Phase 4: donut pie chart for top-N countries
-export function renderPieChart(container, data) {}
+import * as d3 from "https://cdn.jsdelivr.net/npm/d3@7/+esm";
+
+const COLORS = ["#0062ff", "#da1e28", "#fdd13a", "#24ab48", "#9966ff", "#606e85"];
+const SIZE = 420;
+const RADIUS = SIZE / 2 - 30;
+const INNER_RADIUS = RADIUS * 0.45;
+
+// data: [{label, value, alpha3}]  (alpha3 is null for "Rest of World")
+// onSliceClick: (alpha3) => void — called only for named-country slices
+export function renderPieChart(container, data, onSliceClick) {
+	const el = typeof container === "string"
+		? document.querySelector(container)
+		: container;
+
+	el.innerHTML = "";
+
+	const svg = d3.select(el).append("svg")
+		.attr("viewBox", `0 0 ${SIZE} ${SIZE}`)
+		.attr("width", "100%");
+
+	const g = svg.append("g")
+		.attr("transform", `translate(${SIZE / 2},${SIZE / 2 - 10})`);
+
+	const pie = d3.pie().value(d => d.value).sort(null);
+	const arc = d3.arc().outerRadius(RADIUS).innerRadius(INNER_RADIUS);
+	const labelArc = d3.arc()
+		.outerRadius(RADIUS * 0.78)
+		.innerRadius(RADIUS * 0.78);
+
+	const arcs = g.selectAll(".arc")
+		.data(pie(data))
+		.join("g")
+		.attr("class", "arc");
+
+	arcs.append("path")
+		.attr("d", arc)
+		.attr("fill", (d, i) => COLORS[i % COLORS.length])
+		.attr("stroke", "#161616")
+		.attr("stroke-width", 2)
+		.style("cursor", d => d.data.alpha3 ? "pointer" : "default")
+		.on("click", (event, d) => {
+			if (d.data.alpha3 && onSliceClick) onSliceClick(d.data.alpha3);
+		});
+
+	arcs.append("text")
+		.attr("transform", d => `translate(${labelArc.centroid(d)})`)
+		.attr("text-anchor", "middle")
+		.attr("dy", "0.35em")
+		.style("fill", "#fff")
+		.style("font-size", "11px")
+		.style("pointer-events", "none")
+		.text(d => {
+			const angle = d.endAngle - d.startAngle;
+			return angle > 0.3 ? d.data.label : "";
+		});
+
+	// Legend
+	const legend = svg.append("g")
+		.attr("transform", `translate(10, ${SIZE - 20 - data.length * 18})`);
+
+	data.forEach((d, i) => {
+		const row = legend.append("g").attr("transform", `translate(0, ${i * 18})`);
+		row.append("rect").attr("width", 12).attr("height", 12).attr("fill", COLORS[i % COLORS.length]);
+		row.append("text")
+			.attr("x", 16)
+			.attr("y", 10)
+			.style("fill", "#ccc")
+			.style("font-size", "11px")
+			.text(d.label);
+	});
+}