waybar: work around DST bug in built-in clock module

waybar 0.15.0's clock module reads PST instead of PDT, showing time
an hour behind. Replace with custom/exec calling date directly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

waybar/style.css

@@ -19,7 +19,7 @@ window#waybar {
   color: @tn-blue;
 }
 
-#clock, #battery, #network, #pulseaudio,
+#custom-clock, #battery, #network, #pulseaudio,
 #cpu, #temperature,
 #custom-power-profile, #custom-fan-profile {
   padding: 0 12px;