refactor(frontend): concept trees, query runner, query node editor on tailwind-variants

[Kadrian]

Emotion → tailwind migration, PR 2/6: the query-editing core (31 files).

(concept-trees, query-runner, query-node-editor — stacked on #3992, stack overview there)

Main change

• every styled() block → tv(); truly dynamic values (tree depth * 15px indents, drag preview sizes) stay inline style
• QueryRunningSpinner reads the spinner image via useAppTheme(); built-in animate-spin replaces the custom keyframes (identical)

Worth a closer look

• QueryRunnerButton: descendant hover (&:hover .query-runner-label) → named group group/runner + group-hover/runner:; the marker class is gone
• DownloadResultsDropdownButton: nested button {…} selector → [&_button]: variants
• duplicate styled blocks collapsed into variants (error/success icons in both upload modals, error/not-found text states)
• a11y: two clickable non-buttons keep onClick + biome-ignore/TODO instead of invented roles

Checks: biome, tsc, vitest, vite build green; generated css spot-checked (named group-hover, [&_button], bg-size-[30px]).