refactor(frontend): hover tooltips on react-aria-components

[Kadrian]

Design-system prep, step 2: hover tooltips on react-aria-components

Stacked on #3999. WithTooltip (tippy) is replaced by ui-components/Tooltip built on react-aria-components, using its composition shape so the call sites don't change again when more components move to react-aria:

<TooltipTrigger>
  <IconButton … />
  <Tooltip>{t("common.delete")}</Tooltip>
</TooltipTrigger>

Main change

• react-aria-components and react-aria added; tippy stays only for the three click popovers (HelpMenu, DownloadResultsDropdownButton, ConfirmableTooltip), which move to a Popover in the next step
• BasicButton reads the trigger props through useFocusable, so every existing button is a tooltip trigger on its own, without wrappers, and stays one when it becomes a react-aria Button
• TooltipTarget marks non-button content (icons, node labels, dropzones) as the trigger; static content keeps excludeFromTabOrder so the tab order is unchanged, help icons become keyboard reachable
• Tooltip renders nothing without content, so optional texts work as before; wide and placement kept, lazy became delay={1500}
• look kept: white box, shadow, arrow, 100 ms fade (--animate-fade-in/out)
• storybook now loads index.css, first Tooltip stories

Worth a closer look

• tooltips open after 500 ms on first hover and immediately for neighbouring triggers (react-aria's warm-up), and don't open on disabled buttons or on touch
• className on the old WithTooltip styled tippy's box, not the trigger, so those classes were dropped; the whitespace-nowrap one moved onto the Tooltip

Next steps

• Popover for the three click uses, remove tippy
• Button and Icon consolidation in ui-components