refactor(supply): per-unit details always visible + shared editor in unit list AND pre-market

- Extract UnitFieldsEditor (price, availability, Ausbaustandard, Wer-baut-aus, MAB, parking allocation, expected price) — single source for per-unit editing
- UnitStructurePanel: always-visible per-unit details strip (fit-out, cost-bearer, parking, expected price) in read mode; pencil opens the shared editor
- PreMarketUnitGrid: per-unit details shown + same editor reachable per unit (pencil) so fit-out/price/parking are adjustable right in the release flow
- Removes the previous edit-only / fragmented per-unit fields

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/components/supply/PreMarketPanel.tsx

@@ -188,6 +188,7 @@ export function PreMarketPanel({ p }: { p: Property }) {
 
             {(p.units?.length ?? 0) > 0 && (
               <PreMarketUnitGrid
+                property={p}
                 units={p.units!}
                 unitStates={unitStates}
                 unitSaving={unitSaving}