fix(notification): use implicitHeight for banner height, remove wrong dockSize fallback

1. Bubble.qml: add 'height: implicitHeight' so the banner height
   properly updates when content changes (e.g. when a replacement
   notification has body/actions while the original had none).

2. main.qml: remove dockSize fallback for frontendWindowRect.
   dockSize (52) != actual dock height (65 from FrontendWindowRect),
   giving a wrong margin. Return 0 when rect is not ready; the
   Connections block will refresh once it becomes available.

Author: 18202781743

panels/notification/bubble/package/Bubble.qml

@@ -14,6 +14,7 @@ NotifyItemContent {
     property var bubble
 
     width: 360
+    height: implicitHeight
     appName: bubble.appName
     iconName: bubble.iconName
     date: bubble.timeTip

panels/notification/bubble/package/main.qml

@@ -31,15 +31,13 @@ Window {
         if (dockPosition !== position)
             return 0
 
-        let dockSize = dockApplet.dockSize
-
-        // When frontendWindowRect is not yet computed (0,0,0,0), fall back to
-        // dockSize. The Connections block will refresh margins once the rect
-        // becomes available, giving the precise value.
         let frontendRect = dockApplet.frontendWindowRect
+        // frontendWindowRect is not yet computed, return 0 and wait for
+        // the Connections block to refresh once it becomes available.
         if (frontendRect.width === 0 && frontendRect.height === 0)
-            return dockSize
+            return 0
 
+        let dockSize = dockApplet.dockSize
         let dpr = root.screen.devicePixelRatio
         let dockGeometry = Qt.rect(
             frontendRect.x / dpr,