fix: stop overwriting client_traffics.enable with JSON enable in GetClientTrafficByEmail (#3931)
When a client hit traffic/expiry limit, disableInvalidClients sets
client_traffics.enable=false and removes the user from Xray. GetClientTrafficByEmail
was overwriting that with settings.clients[].enable (admin config), so
ResetClientTraffic never saw the client as disabled and did not re-add
the user. Clients could not connect until manually disabled/re-enabled.
Now the DB runtime enable flag is preserved; reset correctly re-adds
the user to Xray.