Show a confirmation dialog when marking all entries as read with keyboard shortcut


### Discussed in https://github.com/Athou/commafeed/discussions/1734

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<sup>Originally posted by **tomhusband** March 22, 2025</sup>
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Make this setting also apply to the `shift+a` keyboard shortcut:

![Image](https://github.com/user-attachments/assets/dcd7c71c-1e50-48cb-9242-3936337cefc0)