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>
Benjamin Sutter