Refine mobileform settings

Numerous refinements to the new mobileform setting pages 
- Ensure left and right padding at the top level is 0 for mobile
- Centre align the avatar in the account editor page and add tooltip to button
- Fix the bubble/compact mode setting so that it fits when thin, i.e on mobile
- Fix the loading placeholder in device settings

src/qml/Settings/NetworkProxyPage.qml

@@ -15,6 +15,8 @@ Kirigami.ScrollablePage {
     property int currentType
     property bool proxyConfigChanged: false
 
+    leftPadding: 0
+    rightPadding: 0
     ColumnLayout {
         MobileForm.FormCard {
             Layout.topMargin: Kirigami.Units.largeSpacing