refactor(frontend): menus on react-aria-components, drop tippy

[Kadrian]

Design-system prep, step 4: menus on react-aria-components, tippy removed

Stacked on #4003. The three click overlays, help menu, download list and the delete/reset confirmations, are menus: a list of actions or links to pick from. They move to react-aria's MenuTrigger with our Menu, and tippy goes.

<MenuTrigger>
  <IconButton … />
  <Menu aria-label="…" onAction={(key) => …}>
    <MenuItem id="…">…</MenuItem>
    <MenuItem href="…">…</MenuItem>
  </Menu>
</MenuTrigger>

• ui-components/Menu: Menu brings its own popover, so all menus share one offset and overflow behaviour and placement is the only knob; MenuItem with danger; items focus on hover, arrow keys move, Enter picks, Escape closes and returns focus
• ConfirmableTooltip → ConfirmMenu, a one-item menu that closes itself after the action
• help menu and download list are link items; menus open below the trigger and flip when there is no room
• tippy packages and CSS overrides removed; the e2e test follows the confirmation into its portal
• Menu stories

[awildturtok]

Das sieht mir nach einer kleinen Änderung aus, hast du geschaut, dass es am Ende nah genug am alten dran ist?