Accessibility and design fixes for update and redirect pages

[jancborchardt]

• Regular links now have an underline effect on hover/focus. Makes more sense than the transparency on hover and looks especially nice in Webkit cause it does not cut through descenders.
• The buttons now have hover/focus state for proper accessibility
• Buttons have proper padding for clickability
• Style update button as primary (blue)

Log in now, with nice hover/focus effect (there was none before):

Redirect of Mail app before & after, had no hover/focus effect either. General style adjusted like the modal in #11536

Same for upgrade, had no hover/focus effect, and some spacing on top and bottom was fixed:

Please review @nextcloud/designers @nextcloud/accessibility

[skjnldsv]

Not really fond of the shadow, feels too strange :)
I feel like when using opacity, having a neat delimitation is easier for us to find where to focus, but the eye tend to get confused by gradual shadow.

But the rest is 🔥 🔥 🔥

[jancborchardt]

@skjnldsv removed the shadow! 🌞

Fiiixed

[MariusBluem]

I liked it more with the shaddow to be honest 🤨🤭

[MorrisJobke]

👍 I like it with the shadow 👍

[jancborchardt]

For the record: I also like it better with the shadow, but am also fine without. :) Let’s just get it in like this, we can do the shadow later.

[weeman1337]

I like it more without the shadow. It somehow looks cleaner.
With shadow this also looks like the new rounded dialogs - but it isn't one...

[rullzer]

Let me merge this now and you can discuss further changes in followup issues :)