Fix issues with the tabs and navigation menus

[RyotaMitaraiWeb]

Addresses #79.

One important thing to note is that the tabs' underline does not have a transition, I suspect this is caused by the component getting destroyed and then mounted again when navigating to a different tab page. Perhaps a global context could be used to bypass this, but I feel like it will be an overkill for little gain (and, technically speaking, this is consistent with the previous variant's behavior).

There may be a few visual changes due to the tabs' default styling, but those should be minor.

I also renamed the component to CardflowTabs to be more generic, could maybe change it to something else.

[julkascript]

The transition is not a problem. We can fix it at a later point if it becomes necessary.