Merge #476: Activity page fixes

ffd0c09 Fix stackView reference in Activity (johnny9)
d92a626 Fix Activity listView's anchors (johnny9)

Pull request description:

  There were two errors that prevented the Activity page from working correctly

  The first was a missing anchor for the listView, The patch correctly has the listView fill its parent so it appears now.

  Before:
  <img width="869" height="716" alt="Screenshot from 2025-07-21 22-57-11" src="https://github.com/user-attachments/assets/21c4801f-831d-4efa-b5d8-28cf49f6eca5" />
  After:
  <img width="869" height="716" alt="Screenshot from 2025-07-21 22-57-18" src="https://github.com/user-attachments/assets/d32b827c-6093-4dae-a0cf-6107c5cff77b" />

  The second fix fixes a bad reference to the stackView and gets rid of the following error in debug.log
  `2025-07-22T02:47:12Z GUI: qrc:/qml/pages/wallet/Activity.qml:19: TypeError: Cannot call method 'pop' of null`

ACKs for top commit:
  pinheadmz:
    ACK ffd0c09

Tree-SHA512: ffb055f74012795a4ffc68b96396e7529fdb6e866e69b81f4907534aef8cbd919126f6967d5b6c5cd0f7495c2a6e65f07a94596ae21cf92d19a76e53fce9d4ff

Author: hebasto

qml/pages/wallet/Activity.qml

@@ -16,7 +16,7 @@ PageStack {
     Connections {
         target: walletController
         function onSelectedWalletChanged() {
-            root.StackView.view.pop()
+            stackView.pop()
         }
     }
 
@@ -87,6 +87,7 @@ PageStack {
 
                 ListView {
                     id: listView
+                    anchors.fill: parent
                     clip: true
                     model: walletController.selectedWallet.activityListModel
                     delegate: ItemDelegate {