feat(supply): per-unit price/availability editor + mandatory fit-out cost-bearer for shell/edelrohbau

- unit.availableFrom: explicit per-unit availability date
- UnitStructurePanel: inline expandable editor (pencil) for per-unit price + availability via useUpdateUnit
- fitOutByLandlord now boolean|undefined ("not chosen"); toggle has no default for SHELL/BASIC
- NewListing: validate() blocks save until cost-bearer chosen for Rohbau/Edelrohbau
- PropertyDetailView.saveEdit: same guard for existing listings; required asterisk + hint in both forms
- newListingMapper persists explicit tenant(false) choice (was collapsed to undefined)

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

src/hooks/useNewListingForm.ts

@@ -15,6 +15,8 @@ function validate(fields: {
   city: string
   areaSqm: string
   rentPerSqm: string
+  fitOut: string
+  fitOutByLandlord: boolean | undefined
 }): string | null {
   if (!fields.street.trim())                                         return 'Strasse erforderlich'
   if (!fields.postalCode.trim())                                     return 'PLZ erforderlich'
@@ -23,6 +25,9 @@ function validate(fields: {
       || Number(fields.areaSqm) <= 0)                               return 'Gültige Fläche eingeben'
   if (!fields.rentPerSqm || isNaN(Number(fields.rentPerSqm))
       || Number(fields.rentPerSqm) <= 0)                            return 'Gültigen Mietpreis eingeben'
+  // Bei Rohbau/Edelrohbau muss der Ausbau-Träger aktiv gewählt werden
+  if ((fields.fitOut === 'SHELL' || fields.fitOut === 'BASIC')
+      && fields.fitOutByLandlord === undefined)                     return 'Bitte wählen, wer den Ausbau trägt (Vermieter oder Mieter)'
   return null
 }
 
@@ -43,7 +48,7 @@ export interface NewListingFormState {
   // Technical
   floor: string
   fitOut: string
-  fitOutByLandlord: boolean
+  fitOutByLandlord: boolean | undefined
   parking: string
   ceilingHeight: string
   mieterausbaubeitrag: string
@@ -81,7 +86,7 @@ export interface NewListingFormHandlers {
   setSoftLevel: (key: string, value: string) => void
   setFloor: (v: string) => void
   setFitOut: (v: string) => void
-  setFitOutByLandlord: (v: boolean) => void
+  setFitOutByLandlord: (v: boolean | undefined) => void
   setParking: (v: string) => void
   setCeilingHeight: (v: string) => void
   setMieterausbaubeitrag: (v: string) => void
@@ -119,7 +124,7 @@ export function useNewListingForm(pre: Prefill): NewListingFormState & NewListin
   const [softLevels,    setSoftLevels]   = useState<Record<string, string>>(() => ({ ...emptySoftLevels(), ...pre.softLevels }))
   const [floor,         setFloor]        = useState(pre.floor ?? '')
   const [fitOut,        setFitOut]       = useState(pre.fitOut ?? '')
-  const [fitOutByLandlord, setFitOutByLandlord] = useState(pre.fitOutByLandlord ?? false)
+  const [fitOutByLandlord, setFitOutByLandlord] = useState<boolean | undefined>(pre.fitOutByLandlord)
   const [parking,       setParking]      = useState(pre.parking != null ? String(pre.parking) : '')
   const [ceilingHeight, setCeilingHeight]= useState(pre.ceilingHeight != null ? String(pre.ceilingHeight) : '')
   const [mieterausbaubeitrag, setMieterausbaubeitrag] = useState(pre.mieterausbaubeitragPerSqm != null ? String(pre.mieterausbaubeitragPerSqm) : '')
@@ -164,7 +169,7 @@ export function useNewListingForm(pre: Prefill): NewListingFormState & NewListin
   }
 
   function handleSubmit() {
-    const err = validate({ street, postalCode, city, areaSqm, rentPerSqm })
+    const err = validate({ street, postalCode, city, areaSqm, rentPerSqm, fitOut, fitOutByLandlord })
     if (err) { setError(err); return }
     setError(null)
     createProperty.mutate(
@@ -188,7 +193,7 @@ export function useNewListingForm(pre: Prefill): NewListingFormState & NewListin
     setAreaSqm(''); setRentPerSqm(''); setAvailableFrom(''); setDescription('')
     setContactName(''); setContactEmail(''); setContactPhone('')
     setSoftLevels(emptySoftLevels())
-    setFloor(''); setFitOut(''); setFitOutByLandlord(false); setParking(''); setCeilingHeight('')
+    setFloor(''); setFitOut(''); setFitOutByLandlord(undefined); setParking(''); setCeilingHeight('')
     setMieterausbaubeitrag(''); setIsFlexible(false); setMinLettableSqm('')
     setImages([]); setImageInput(''); setFloorPlanUrl('')
     setAiText(''); setAiApplied(false)