Fix operations panel list not growing on resize (#4947)

[Gabriel Dufresne (GabrielDuf)]

This pull request improves the user experience of the operations panel in the main window by making its height resizable and persistent across expand/collapse actions. The key changes ensure that when the panel is expanded, it restores the last user-chosen height, and when collapsed, it saves the current height and collapses the panel cleanly. The grid layout and event handling have been updated to support this behavior.

Operations panel resizability and persistence:

• Changed the operations panel grid's row definition from two auto-sized rows to one auto and one star-sized row, enabling flexible height adjustment. (src/UniGetUI.Avalonia/Views/MainWindow.axaml)
• Removed the fixed MaxHeight constraint from the operations panel's ScrollViewer, allowing the panel to expand as needed. (src/UniGetUI.Avalonia/Views/MainWindow.axaml)
• Added a private _operationsPanelHeight field to store the last user-selected height of the operations panel, and logic to restore this value when the panel is re-expanded. (src/UniGetUI.Avalonia/Views/MainWindow.axaml.cs)
• Subscribed to ViewModel.PropertyChanged to detect changes to the operations panel's visibility and expansion state, triggering updates to the panel's grid row. (src/UniGetUI.Avalonia/Views/MainWindow.axaml.cs)
• Implemented the UpdateOperationsPanelRow method to manage the grid row's height and minimum height, ensuring the panel's size is preserved across state changes. (src/UniGetUI.Avalonia/Views/MainWindow.axaml.cs)