[Feature Request] Make Shortcuts Tab Bar Position Configurable

**Describe the bug**

By default the tab bar with shortcuts is displayed at the bottom of the screen for smaller widths and at the top for larger viewports. This can not be what the user expects / desires, e.g. on on a vertical iPad Mini, I’d expect the shortcuts to be at the bottom for easier reach (they are at the top), while in a narrow window to the side on desktop, I’d want them at the top.

- Which site: dev.phanpy.social
- Which instance: mastodon.design

**To Reproduce**

Enable shortcuts, have them display as tabs and scale the window size / open the site on a small tablet.

**Expected behavior**

I’d expect the positioning of the tab bar to follow platform conventions and not be tied to device size.

**Additional context**

I think instead of trying to be smart about the positioning by figuring out in what device Phanpy is running on, there could just be an additional option in the shortcut settings to specify where the bar (and perhaps even the action button) should be placed.

Thank you for the time and effort you’re putting into this client! 😊

Start by tracing the shortcut settings and the responsive code that places the tab bar at the top or bottom, then reproduce the behavior on a narrow window and small tablet. Done means users can configure the tab-bar position independently of viewport size; whether the action button follows should be clarified before implementation.

Written by the indexing model from the issue text.