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.

3 files changed, 78 insertions, 6 deletions

diff --git a/assets/js/map/choropleth.js b/assets/js/map/choropleth.js
index 9316f29..5262764 100644
--- a/assets/js/map/choropleth.js
+++ b/assets/js/map/choropleth.js
@@ -10,6 +10,7 @@ const NO_DATA_FILL = "#444";
 let svg, mapGroup, projection, pathGen, features;
 let _countries, _isoLookup;
 let _clickHandler = null;
+let _labelsVisible = false;
 
 export async function initMap(container, countries, isoLookup) {
 	_countries = countries;
@@ -43,9 +44,33 @@ export async function initMap(container, countries, isoLookup) {
 			if (_clickHandler) _clickHandler(event, d);
 		});
 
+	// Country name labels, hidden by default
+	mapGroup.selectAll("text.country-label")
+		.data(features)
+		.join("text")
+		.attr("class", "country-label")
+		.attr("transform", d => {
+			const [x, y] = pathGen.centroid(d);
+			return isNaN(x) || isNaN(y) ? "translate(-9999,-9999)" : `translate(${x},${y})`;
+		})
+		.attr("text-anchor", "middle")
+		.attr("dy", "0.35em")
+		.style("font-size", "7px")
+		.style("fill", "#fff")
+		.style("pointer-events", "none")
+		.style("display", "none")
+		.text(d => {
+			const alpha3 = _isoLookup[+d.id];
+			return alpha3 && _countries[alpha3] ? _countries[alpha3].country : "";
+		});
+
 	return { svg, mapGroup, projection };
 }
 
+export function getCountryPaths() {
+	return mapGroup.selectAll("path.country");
+}
+
 export function applyGradient(metricKey) {
 	const values = Object.values(_countries)
 		.map(c => c[metricKey])
@@ -69,6 +94,12 @@ export function resetGradient() {
 		.attr("fill", d => _fillForFeature(d, null, null));
 }
 
+export function toggleLabels() {
+	_labelsVisible = !_labelsVisible;
+	mapGroup.selectAll("text.country-label")
+		.style("display", _labelsVisible ? "block" : "none");
+}
+
 export function setClickHandler(fn) {
 	_clickHandler = fn;
 }
diff --git a/assets/js/map/tooltip.js b/assets/js/map/tooltip.js
index c8f112a..c74418b 100644
--- a/assets/js/map/tooltip.js
+++ b/assets/js/map/tooltip.js
@@ -1,3 +1,29 @@
-// Phase 3: hover tooltip
-export function initTooltip() {}
-export function attachTooltip(selection, getContent) {}
+import * as d3 from "https://cdn.jsdelivr.net/npm/d3@7/+esm";
+
+let tooltip;
+
+export function initTooltip() {
+	tooltip = d3.select("body")
+		.append("div")
+		.attr("class", "map-tooltip");
+}
+
+export function attachTooltip(selection, getContent) {
+	selection
+		.on("mouseover", (event, d) => {
+			const content = getContent(event, d);
+			if (content) {
+				tooltip.style("opacity", 1).html(content);
+			} else {
+				tooltip.style("opacity", 0);
+			}
+		})
+		.on("mousemove", (event) => {
+			tooltip
+				.style("left", (event.pageX + 12) + "px")
+				.style("top", (event.pageY - 28) + "px");
+		})
+		.on("mouseout", () => {
+			tooltip.style("opacity", 0);
+		});
+}
diff --git a/assets/js/map/zoom.js b/assets/js/map/zoom.js
index aec278b..cba7c2c 100644
--- a/assets/js/map/zoom.js
+++ b/assets/js/map/zoom.js
@@ -1,3 +1,18 @@
-// Phase 3: zoom and pan behavior
-export function initZoom(svg, mapGroup) {}
-export function resetZoom(svg, zoomBehavior) {}
+import * as d3 from "https://cdn.jsdelivr.net/npm/d3@7/+esm";
+
+let _svg, _zoom;
+
+export function initZoom(svg, mapGroup) {
+	_svg = svg;
+	_zoom = d3.zoom()
+		.scaleExtent([0.5, 8])
+		.on("zoom", (event) => {
+			mapGroup.attr("transform", event.transform);
+		});
+	svg.call(_zoom);
+	return _zoom;
+}
+
+export function resetZoom() {
+	_svg.transition().duration(750).call(_zoom.transform, d3.zoomIdentity);
+}