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>

frontend/src/stores/property.ts

@@ -0,0 +1,55 @@
+import { defineStore } from 'pinia'
+import { ref, computed } from 'vue'
+import { propertiesApi } from '@/services/api'
+import { useAuthStore } from './auth'
+import type { Property } from '@/types'
+
+export const usePropertyStore = defineStore('property', () => {
+  const properties = ref<Property[]>([])
+  const currentPropertyId = ref<number | null>(
+    localStorage.getItem('currentPropertyId')
+      ? Number(localStorage.getItem('currentPropertyId'))
+      : null
+  )
+  const loading = ref(false)
+
+  const currentProperty = computed(() =>
+    properties.value.find(p => p.id === currentPropertyId.value) || null
+  )
+
+  const setCurrentProperty = (id: number | null) => {
+    currentPropertyId.value = id
+    if (id) {
+      localStorage.setItem('currentPropertyId', String(id))
+    } else {
+      localStorage.removeItem('currentPropertyId')
+    }
+  }
+
+  const fetchMyProperties = async () => {
+    loading.value = true
+    try {
+      const authStore = useAuthStore()
+      if (authStore.isSuperadmin) {
+        properties.value = await propertiesApi.listAll()
+      } else {
+        properties.value = await propertiesApi.list()
+      }
+      // Auto-select first property if none selected
+      if (!currentPropertyId.value && properties.value.length > 0) {
+        setCurrentProperty(properties.value[0].id)
+      }
+    } finally {
+      loading.value = false
+    }
+  }
+
+  return {
+    properties,
+    currentPropertyId,
+    currentProperty,
+    loading,
+    setCurrentProperty,
+    fetchMyProperties
+  }
+})