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.

1 files changed, 18 insertions, 3 deletions

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);
+}