Fix mobile view Bugs and add versions to static files for cache breaking

public/js/slideshow.js

@@ -5,6 +5,12 @@
   let index = 0;
   let swipe = null;
 
+  function mediaUrl(url) {
+    if (!url) return '';
+    const separator = url.includes('?') ? '&' : '?';
+    return `${url}${separator}v=${Date.now()}`;
+  }
+
   function activate(selector, handler) {
     $(document)
       .on('pointerup', selector, function (event) {
@@ -33,8 +39,12 @@
 
     const image = images[index];
     $('#slide-image')
-      .attr('src', image.url)
-      .attr('alt', image.caption || 'Bild zur Station');
+      .attr('src', mediaUrl(image.url))
+      .attr('alt', image.caption || 'Bild zur Station')
+      .off('error.wegwichtel')
+      .on('error.wegwichtel', function () {
+        $(this).removeAttr('src').attr('alt', 'Bild konnte nicht geladen werden');
+      });
     $('#slide-caption').text(image.caption || '');
     $('#slide-position').text(`${index + 1} / ${images.length}`);
     refreshButton('#slide-prev', images.length < 2);