feat: add multi-tenant system with properties, organizations, and public booking

Implement complete multi-property architecture:
- Properties (groups of spaces) with public/private visibility
- Property managers (many-to-many) with role-based permissions
- Organizations with member management
- Anonymous/guest booking support via public API (/api/public/*)
- Property-scoped spaces, bookings, and settings
- Frontend: property selector, organization management, public booking views
- Migration script and updated seed data

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

backend/app/models/property_settings.py

@@ -0,0 +1,20 @@
+"""PropertySettings model."""
+from sqlalchemy import Boolean, Column, ForeignKey, Integer
+
+from app.db.session import Base
+
+
+class PropertySettings(Base):
+    """Per-property scheduling settings."""
+
+    __tablename__ = "property_settings"
+
+    id = Column(Integer, primary_key=True, index=True)
+    property_id = Column(Integer, ForeignKey("properties.id"), nullable=False, unique=True, index=True)
+    working_hours_start = Column(Integer, nullable=True)
+    working_hours_end = Column(Integer, nullable=True)
+    min_duration_minutes = Column(Integer, nullable=True)
+    max_duration_minutes = Column(Integer, nullable=True)
+    max_bookings_per_day_per_user = Column(Integer, nullable=True)
+    require_approval = Column(Boolean, default=True, nullable=False)
+    min_hours_before_cancel = Column(Integer, nullable=True)