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, 22 insertions, 0 deletions

diff --git a/assets/css/app.css b/assets/css/app.css
index 95310fb..af5e95c 100644
--- a/assets/css/app.css
+++ b/assets/css/app.css
@@ -120,4 +120,26 @@ th {
 	pointer-events: none;
 	font-size: 13px;
 	opacity: 0;
+	transition: opacity 0.1s;
+	z-index: 9999;
+}
+
+/* chart containers inside graph modal */
+#myChart2,
+#myNextChart {
+	min-height: 300px;
+	background: #000;
+}
+
+/* active metric button highlight */
+.active-metric {
+	outline: 2px solid #fff;
+}
+
+/* D3 axis lines */
+#myChart2 .domain,
+#myNextChart .domain,
+#myChart2 .tick line,
+#myNextChart .tick line {
+	stroke: #555;
 }