Bump textual to 0.42.0

ft. https://github.com/Textualize/textual/releases/tag/v0.42.0

Important (IMO) changes for us:

• Breaking change: max/min-width/height now includes padding and border
• Breaking change: Button no longer inherits from Static, now it inherits directly from Widget
• Breaking change: Setting Select.value to None no longer clears the selection (See Select.BLANK and Select.clear)
• Fixed live-reloading of screen CSS
• Fixed ScrollableContainer to receive focus

This MR:

• Bump textual to 0.42.0
• Fix a bug where it was impossible to save transaction twice from TransactionSummary screen using different keys (was already signed)
• Fix a bug when activation screen was not showed when saving to file/broadcasting in inactive mode (instead there was an error notification)
• Fix a bug when dashboard was always changed to Active version when activation failed
• Fix possible bug in Activation when error could occur