function openCentreModal(idx){
fetch('../data/centres.json').then(function(r){return r.json()}).then(function(centres){
var active=centres.filter(function(c){return c.status==='active'});
var centre=active[idx];
if(!centre) return;
var name=centre.type==='showroom'?centre.name:'Centre InfraBike '+centre.city;
var html=''+(centre.type==='showroom'?'Offizieller Showroom':'Partnerzentrum')+''+name+''+centre.address+'