Add TenantCustomTier system and fix BusinessEditModal feature loading

Backend:
- Add TenantCustomTier model for per-tenant feature overrides
- Update EntitlementService to check custom tier before plan features
- Add custom_tier action on TenantViewSet (GET/PUT/DELETE)
- Add Celery task for grace period management (30-day expiry)

Frontend:
- Add DynamicFeaturesEditor component for dynamic feature management
- Fix BusinessEditModal to load features from plan defaults when no custom tier
- Update limits (max_users, max_resources, etc.) to use featureValues
- Remove outdated canonical feature check from FeaturePicker (removes warning icons)
- Add useBillingPlans hook for accessing billing system data
- Add custom tier API functions to platform.ts

Features now follow consistent rules:
- Load from plan defaults when no custom tier exists
- Load from custom tier when one exists
- Reset to plan defaults when plan changes
- Save to custom tier on edit

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/hooks/useLocations.ts

@@ -0,0 +1,153 @@
+/**
+ * Location Management Hooks
+ *
+ * Provides hooks for managing business locations in a multi-location setup.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import apiClient from '../api/client';
+import { Location } from '../types';
+
+interface LocationFilters {
+  includeInactive?: boolean;
+}
+
+/**
+ * Hook to fetch locations with optional inactive filter
+ */
+export const useLocations = (filters?: LocationFilters) => {
+  return useQuery<Location[]>({
+    queryKey: ['locations', filters],
+    queryFn: async () => {
+      let url = '/locations/';
+      if (filters?.includeInactive) {
+        url += '?include_inactive=true';
+      }
+      const { data } = await apiClient.get(url);
+      return data;
+    },
+  });
+};
+
+/**
+ * Hook to get a single location by ID
+ */
+export const useLocation = (id: number | undefined) => {
+  return useQuery<Location>({
+    queryKey: ['locations', id],
+    queryFn: async () => {
+      const { data } = await apiClient.get(`/locations/${id}/`);
+      return data;
+    },
+    enabled: id !== undefined,
+  });
+};
+
+/**
+ * Hook to create a new location
+ */
+export const useCreateLocation = () => {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: async (locationData: Partial<Location>) => {
+      const { data } = await apiClient.post('/locations/', locationData);
+      return data;
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['locations'] });
+    },
+  });
+};
+
+/**
+ * Hook to update a location
+ */
+export const useUpdateLocation = () => {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: async ({ id, updates }: { id: number; updates: Partial<Location> }) => {
+      const { data } = await apiClient.patch(`/locations/${id}/`, updates);
+      return data;
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['locations'] });
+    },
+  });
+};
+
+/**
+ * Hook to delete a location
+ */
+export const useDeleteLocation = () => {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: async (id: number) => {
+      await apiClient.delete(`/locations/${id}/`);
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['locations'] });
+    },
+  });
+};
+
+/**
+ * Hook to set a location as primary
+ */
+export const useSetPrimaryLocation = () => {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: async (id: number) => {
+      const { data } = await apiClient.post(`/locations/${id}/set_primary/`);
+      return data;
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['locations'] });
+    },
+  });
+};
+
+/**
+ * Hook to activate or deactivate a location
+ */
+export const useSetLocationActive = () => {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: async ({ id, isActive }: { id: number; isActive: boolean }) => {
+      const { data } = await apiClient.post(`/locations/${id}/set_active/`, {
+        is_active: isActive,
+      });
+      return data;
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['locations'] });
+    },
+  });
+};
+
+/**
+ * Hook to get only active locations (convenience wrapper)
+ */
+export const useActiveLocations = () => {
+  return useLocations();
+};
+
+/**
+ * Hook to get all locations including inactive
+ */
+export const useAllLocations = () => {
+  return useLocations({ includeInactive: true });
+};
+
+/**
+ * Hook to get the primary location
+ */
+export const usePrimaryLocation = () => {
+  const { data: locations, ...rest } = useLocations();
+  const primaryLocation = locations?.find(loc => loc.is_primary);
+  return { data: primaryLocation, locations, ...rest };
+};