style: Style settings modal for dark, black, and red themes

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

webclient/src/Style-black.css

@@ -86,3 +86,18 @@
 	border-color: #bbb;
 	color: #ddd;
 }
+
+.black .modal-content {
+	background: #222;
+	border-color: #828282;
+	color: #ddd;
+}
+
+.black .modal-content button {
+	background-color: #444444;
+	border-color: #bbb;
+}
+
+.black .modal-content button.active {
+	background-color: #555;
+}

webclient/src/Style-dark.css

@@ -82,3 +82,18 @@
 	border-color: #bbb;
 	color: #ddd;
 }
+
+.dark .modal-content {
+	background: #333;
+	border-color: #828282;
+	color: #ddd;
+}
+
+.dark .modal-content button {
+	background-color: #444444;
+	border-color: #bbb;
+}
+
+.dark .modal-content button.active {
+	background-color: #555;
+}

webclient/src/Style-red.css

@@ -104,3 +104,18 @@
 	border-color: #b00;
 	color: #d00;
 }
+
+.red .modal-content {
+	background: #300;
+	border-color: #690000;
+	color: #b00;
+}
+
+.red .modal-content button {
+	background-color: #440000;
+	border-color: #b00;
+}
+
+.red .modal-content button.active {
+	background-color: #550000;
+}