fix: resolve PulseAudio/WirePlumber deadlock and freeze issues

- Fix AudioBackend destructor: properly lock the PA mainloop before
  disconnecting the context to prevent race conditions with PA callbacks

- Fix context leak on reconnect: call pa_context_unref() when the old
  context is replaced after PA_CONTEXT_FAILED to avoid resource leaks

- Fix PA mainloop killed on reconnect (critical): PA_CONTEXT_TERMINATED
  was unconditionally calling quit() on the mainloop, even during
  reconnection when the old context fires TERMINATED after the new one
  was created. This was killing the new context and preventing successful
  reconnection, causing Waybar to appear frozen. The fix only quits
  the mainloop when the terminating context is still the active one.

- Fix Wireplumber use-after-free: explicitly disconnect GObject signal
  handlers for mixer_api_, def_nodes_api_, and om_ before clearing the
  object references in the destructor to prevent callbacks from firing
  with a destroyed self pointer.

- Fix GVariant memory leak in Wireplumber::handleScroll: unref the
  GVariant created for the set-volume signal after the emit call.

Co-authored-by: Alexays <13947260+Alexays@users.noreply.github.com>

src/modules/wireplumber.cpp

@@ -54,6 +54,15 @@ waybar::modules::Wireplumber::Wireplumber(const std::string& id, const Json::Val
 
 waybar::modules::Wireplumber::~Wireplumber() {
   waybar::modules::Wireplumber::modules.remove(this);
+  if (mixer_api_ != nullptr) {
+    g_signal_handlers_disconnect_by_data(mixer_api_, this);
+  }
+  if (def_nodes_api_ != nullptr) {
+    g_signal_handlers_disconnect_by_data(def_nodes_api_, this);
+  }
+  if (om_ != nullptr) {
+    g_signal_handlers_disconnect_by_data(om_, this);
+  }
   wp_core_disconnect(wp_core_);
   g_clear_pointer(&apis_, g_ptr_array_unref);
   g_clear_object(&om_);
@@ -528,6 +537,7 @@ bool waybar::modules::Wireplumber::handleScroll(GdkEventScroll* e) {
     GVariant* variant = g_variant_new_double(newVol);
     gboolean ret;
     g_signal_emit_by_name(mixer_api_, "set-volume", node_id_, variant, &ret);
+    g_variant_unref(variant);
   }
   return true;
 }