fix(waybar): clock tooltip uses single chrono format block

Two bare `{:%…}` specs emptied the hover tooltip (box with no text).
One strftime block with an embedded newline shows date + zone; ensure
tooltip label colors on generated + summer bars.

themes/summer-day/waybar.css

@@ -152,3 +152,10 @@ window#waybar {
 #custom-nightlight,
 #custom-vpn,
 #custom-notification { font-size: 17px; }
+
+tooltip {
+  background: @bg0;
+  border: 1px solid @grey1;
+  border-radius: 8px;
+}
+tooltip label { color: @fg; }