[management] Add user approval (#4411)

This PR adds user approval functionality to the management system, allowing administrators to manually approve new users joining via domain matching. When enabled, users are blocked with pending approval status until explicitly approved by an admin.

Adds UserApprovalRequired setting to control manual user approval requirement
Introduces user approval and rejection endpoints with corresponding business logic
Prevents pending approval users from adding peers or logging in

management/server/activity/codes.go

@@ -177,6 +177,8 @@ const (
 
 	AccountNetworkRangeUpdated Activity = 87
 	PeerIPUpdated              Activity = 88
+	UserApproved               Activity = 89
+	UserRejected               Activity = 90
 
 	AccountDeleted Activity = 99999
 )
@@ -284,6 +286,8 @@ var activityMap = map[Activity]Code{
 	AccountNetworkRangeUpdated: {"Account network range updated", "account.network.range.update"},
 
 	PeerIPUpdated: {"Peer IP updated", "peer.ip.update"},
+	UserApproved:  {"User approved", "user.approve"},
+	UserRejected:  {"User rejected", "user.reject"},
 }
 
 // StringCode returns a string code of the activity