[Feature] Customize the default page that opens when you start the software

[jocmp]

Discussed in #1132

^{Originally posted by goddaneel May 1, 2025}
When I go into a subscription or catalog to read it and exit, it will still be the same subscription or catalog when I go back in.
But I'm used to going to the "All" page when I start the program to make sure I haven't missed a message.
So I'd like to be able to customize the page that the software starts on, so that no matter how I exit or start it, it will go to the customized page by default.