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, 70 insertions, 2 deletions

diff --git a/assets/js/ui/compare.js b/assets/js/ui/compare.js
index d933609..3b0a8bb 100644
--- a/assets/js/ui/compare.js
+++ b/assets/js/ui/compare.js
@@ -1,2 +1,70 @@
-// Phase 5: side-by-side country comparison panel
-export function initCompare(countries) {}
+let _pendingResult = false;
+
+export function initCompare(countries) {
+	const opts = Object.entries(countries)
+		.sort((a, b) => a[1].country.localeCompare(b[1].country))
+		.map(([key, val]) => `<option value="${key}">${val.country}</option>`)
+		.join("");
+
+	document.getElementById("compare-select-1").innerHTML = opts;
+	document.getElementById("compare-select-2").innerHTML = opts;
+
+	document.getElementById("compare-go-btn").addEventListener("click", () => {
+		const k1 = document.getElementById("compare-select-1").value;
+		const k2 = document.getElementById("compare-select-2").value;
+
+		if (k1 === k2) {
+			document.getElementById("compare-alert").innerHTML =
+				"<div class='alert alert-danger'>Please select two different countries.</div>";
+			return;
+		}
+		document.getElementById("compare-alert").innerHTML = "";
+		_prepareResult(countries[k1], countries[k2]);
+		_pendingResult = true;
+		const cm = document.getElementById("compareModal");
+		(bootstrap.Modal.getInstance(cm) || new bootstrap.Modal(cm)).hide();
+	});
+
+	// Show result modal only after compareModal finishes hiding
+	document.getElementById("compareModal").addEventListener("hidden.bs.modal", () => {
+		if (_pendingResult) {
+			_pendingResult = false;
+			const rm = document.getElementById("compareResultModal");
+			(bootstrap.Modal.getInstance(rm) || new bootstrap.Modal(rm)).show();
+		}
+	});
+}
+
+function _prepareResult(c1, c2) {
+	document.getElementById("compare-result-c1").textContent = c1.country;
+	document.getElementById("compare-result-c2").textContent = c2.country;
+
+	const rows = [
+		["Prison Population", _fmt(c1.pop, "pop"),       _fmt(c2.pop, "pop")],
+		["Rate per 100,000",  _fmt(c1.rate, "rate"),     _fmt(c2.rate, "rate")],
+		["Females",           _fmt(c1.females, "pct"),   _fmt(c2.females, "pct")],
+		["Juveniles",         _fmt(c1.juveniles, "pct"), _fmt(c2.juveniles, "pct")],
+		["Occupancy",         _fmt(c1.occupancy, "pct"), _fmt(c2.occupancy, "pct")],
+		["Government",        _fmtGov(c1.government),   _fmtGov(c2.government)],
+	];
+
+	document.getElementById("compare-result-body").innerHTML = rows
+		.map(([label, v1, v2]) =>
+			`<tr><td><b>${label}</b></td><td>${v1}</td><td>${v2}</td></tr>`
+		)
+		.join("");
+}
+
+function _fmt(val, type) {
+	if (val === "--" || val === null || val === undefined || (typeof val === "number" && isNaN(val))) {
+		return "<span class='text-danger'>N/A</span>";
+	}
+	if (type === "pop") return Number(val).toLocaleString("en");
+	if (type === "rate") return String(val);
+	if (type === "pct") return (val * 100).toFixed(2) + " %";
+	return String(val);
+}
+
+function _fmtGov(val) {
+	return (!val || val === "--") ? "<span class='text-danger'>N/A</span>" : val;
+}