Implement Phase 2 audit logging

Add audit logging for admin settings changes, rate limit config updates, anomaly detection config changes (skipped due to no UI), and version cleanup settings updates. Implement logging via central logAdminAction helper and integrate into AdminSettings, VersionCleanupSettings, and RateLimitAlerts mutations (create, update, delete).

src/hooks/useAdminSettings.ts

@@ -49,6 +49,10 @@ export function useAdminSettings() {
 
   const updateSettingMutation = useMutation({
     mutationFn: async ({ key, value }: { key: string; value: unknown }) => {
+      // Get old value for audit log
+      const oldSetting = settings?.find(s => s.setting_key === key);
+      const oldValue = oldSetting?.setting_value;
+      
       const { error } = await supabase
         .from('admin_settings')
         .update({ 
@@ -59,10 +63,19 @@ export function useAdminSettings() {
         .eq('setting_key', key);
       
       if (error) throw error;
-      return { key, value };
+      return { key, value, oldValue };
     },
-    onSuccess: () => {
+    onSuccess: async (data) => {
       queryClient.invalidateQueries({ queryKey: ['admin-settings'] });
+      
+      // Log to audit trail
+      const { logAdminAction } = await import('@/lib/adminActionAuditHelpers');
+      await logAdminAction('admin_setting_updated', {
+        setting_key: data.key,
+        old_value: data.oldValue,
+        new_value: data.value,
+      });
+      
       toast({
         title: "Setting Updated",
         description: "The setting has been saved successfully.",