Fancy effects: fix container positioning

imports/NeoChat/Component/FancyEffectsContainer.qml

@@ -176,12 +176,13 @@ Item {
         repeat: true
         onTriggered: {
             customEmit(Math.random() * parent.width,
-                       Math.random() * parent.width) // height is 0 somehow
+                       Math.random() * parent.height)
         }
     }
 
     ParticleSystem {
         id: fireworksSystem
+        anchors.fill: parent
         running: fireworksInternalTimer.running
         onRunningChanged: {
             if (running) {

imports/NeoChat/Page/RoomPage.qml

@@ -595,11 +595,9 @@ Kirigami.ScrollablePage {
         Layout.fillWidth: true
     }
 
-    FancyEffectsContainer {
+    background: FancyEffectsContainer {
         id: fancyEffectsContainer
 
-        Layout.fillWidth: true
-        Layout.fillHeight: true
         enabled: Config.showFancyEffects
 
         function processFancyEffectsReason(fancyEffect) {