refactor(frontend): standard query editor, previous queries, editor v2 on tailwind-variants

[Kadrian]

Emotion → tailwind migration, PR 3/6: both query editors and the project list (35 files).

(standard-query-editor, previous-queries, editor-v2 — stacked on #3993, stack overview in #3992)

Main change

• every styled() block → tv(); dynamic values (chart palette colours in TimeConnection via useAppTheme(), computed paddings) stay inline style
• EditorLayout.ts → .tsx: its exported Grid/Connector styled components are components now

Worth a closer look

• TreeNode (editor-v2) and ProjectItem: many-flag border/padding logic → variants with order-encoded precedence (commented inline)
• descendant-selector hover → named group (folder delete button, group/folder); EmptyQueryEditorDropzone uses [grid-template-areas:…] arbitrary properties
• three tv-const/prop shadowing crashes caught in review (group, label/description, resultCount) — renamed consts
• isAnd on QueryEditorDropzone is no longer forwarded (it only ever fed the styled wrapper; emotion swallowed it)
• word-break: break-word kept literally as [word-break:break-word] (tailwind's break-words is overflow-wrap, a different declaration)

Checks: biome, tsc, vitest, vite build green; generated css spot-checked (group-hover/folder, grid areas, word-break).