refactor: migrate complex-tooltip modules to ALabel dedup setters

Switch direct label_.set_markup/set_tooltip_markup calls to the
deduplicating setLabelMarkup/setTooltipMarkup helpers in clock, custom
and mpris, keeping their custom tooltip construction logic intact.
taskbar is left untouched: its tooltip lives on per-task Gtk::Button,
not on an ALabel label_.

src/modules/custom.cpp

@@ -187,7 +187,7 @@ auto waybar::modules::Custom::update() -> void {
       if ((config_["hide-empty-text"].asBool() && text_.empty()) || str.empty()) {
         event_box_.hide();
       } else {
-        label_.set_markup(str);
+        setLabelMarkup(str);
         if (tooltipEnabled()) {
           std::string tooltip_markup;
           if (tooltip_format_enabled_) {
@@ -202,10 +202,7 @@ auto waybar::modules::Custom::update() -> void {
             tooltip_markup = tooltip_;
           }
 
-          if (last_tooltip_markup_ != tooltip_markup) {
-            label_.set_tooltip_markup(tooltip_markup);
-            last_tooltip_markup_ = std::move(tooltip_markup);
-          }
+          setTooltipMarkup(tooltip_markup);
         }
         auto style = label_.get_style_context();
         auto classes = style->list_classes();