refactor: unit-centric lease view — Einheiten & Mietverträge

Replace building-level Miet- & Mieterinformationen section with
unit-level lease display. Each unit row now shows tenant name and
lease end date directly; expand reveals full contract details
(Mietbeginn, Mietende, Laufzeit, Breakout, source system, doc link).

Floor grouping groups consecutive same-floor units under one label.
Domain model extended with Lease and Tenant types; deprecated
property-level tenant fields preserved via @deprecated for compat.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/domain/property.ts

@@ -4,6 +4,7 @@ import type {
 } from './enums'
 import { AvailabilityStatus as AS } from './enums'
 import type { PropertyUnit } from './unit'
+import type { Lease } from './lease'
 
 // Re-export unit types so all existing imports from 'property' continue to work
 export type { PropertyUnit, UnitBundle, UnitNeedMatch } from './unit'
@@ -137,18 +138,26 @@ export interface Property {
   description?: string
   images?: string[]
   floorPlanUrl?: string
-  leaseContractUrl?: string    // link to the signed lease document
-  leaseContractName?: string   // display label, e.g. "Mietvertrag 2021–2026"
+  /** @deprecated Use unit.leases[].contractDocumentUrl instead */
+  leaseContractUrl?: string
+  /** @deprecated Use unit.leases[].contractDocumentName instead */
+  leaseContractName?: string
 
   propertyNumber?: string
   units?: PropertyUnit[]
   mapImageUrl?: string
 
+  /** @deprecated Use unit.leases instead */
   leaseTerm?: string
+  /** @deprecated Use unit.leases[].startDate instead */
   leaseStartDate?: string
+  /** @deprecated Use unit.leases[].endDate instead */
   leaseEndDate?: string
+  /** @deprecated Use unit.leases[].breakoutOption instead */
   breakoutOption?: boolean
+  /** @deprecated Use unit.leases[].breakoutOptionDate instead */
   breakoutOptionDate?: string
+  /** @deprecated Use unit.leases[].tenant.companyName instead */
   currentTenant?: string
   importedFrom?: string
   importedAt?: string
@@ -169,9 +178,29 @@ export type UpdatePropertyInput = Partial<CreatePropertyInput>
  * Returns the rentable units of a property.
  * For properties without explicit units, synthesises one unit from property-level data
  * so that all matching logic can operate uniformly at unit level.
+ * Property-level lease fields are synthesised into a proper Lease object for backward compat.
  */
 export function getEffectiveUnits(p: Property): PropertyUnit[] {
   if (p.units && p.units.length > 0) return p.units
+
+  const syntheticLease: Lease | undefined = p.currentTenant
+    ? {
+        id: `${p.id}-lease`,
+        unitId: p.id,
+        tenant: { id: `${p.id}-tenant`, companyName: p.currentTenant },
+        rentPerSqm: p.rentPricePerSqm,
+        startDate: p.leaseStartDate ?? '',
+        endDate: p.leaseEndDate ?? '',
+        contractDurationYears: p.contractDurationMonths ? Math.round(p.contractDurationMonths / 12) : undefined,
+        breakoutOption: p.breakoutOption,
+        breakoutOptionDate: p.breakoutOptionDate,
+        status: p.leaseEndDate && new Date(p.leaseEndDate) > new Date() ? 'ACTIVE' : 'EXPIRED',
+        sourceSystem: p.importedFrom ?? 'MANUAL',
+        contractDocumentUrl: p.leaseContractUrl,
+        contractDocumentName: p.leaseContractName,
+      }
+    : undefined
+
   return [{
     id: p.id,
     propertyId: p.id,
@@ -180,9 +209,7 @@ export function getEffectiveUnits(p: Property): PropertyUnit[] {
     areaSqm: p.areaSqm,
     available: p.availabilityStatus === AS.AVAILABLE_NOW || p.availabilityStatus === AS.AVAILABLE_SOON,
     rentPricePerSqm: p.rentPricePerSqm,
-    currentTenant: p.currentTenant,
-    leaseTerm: p.leaseTerm,
-    leaseEndDate: p.leaseEndDate,
+    leases: syntheticLease ? [syntheticLease] : [],
     schattenmarktRelease: p.schattenmarktRelease?.enabled
       ? { enabled: true, availableFrom: p.leaseEndDate }
       : undefined,