Improve modals in dark mode via a dark backdrop and shadow.

frontend/src/App.css

@@ -13,6 +13,15 @@
 	--tblr-backdrop-opacity: 0.8 !important;
 }
 
+[data-bs-theme="dark"] .modal-content {
+	--tblr-modal-box-shadow: 0 0.5rem 1rem rgba(0, 0, 0, 0.15) !important;
+}
+
+[data-bs-theme="dark"] .modal-backdrop {
+	--tblr-backdrop-bg: #000 !important;
+	--tblr-backdrop-opacity: 0.65 !important;
+}
+
 .domain-name {
 	font-family: monospace;
 }