fix(preview): show fallback when image loading fails

Signed-off-by: Sebastian <krupinski01@gmail.com>

src/components/ImageViewer.vue

@@ -3,6 +3,7 @@ import { ref, computed, onMounted, onUnmounted } from 'vue'
 import type { MediaLeafProps } from '@/types'
 
 const props = defineProps<MediaLeafProps>()
+const emit = defineEmits<{ error: [] }>()
 
 // ── Pan / zoom state ────────────────────────────────────────────────────────
 
@@ -103,6 +104,7 @@ onUnmounted(() => {
         transformOrigin: 'center center',
       }"
       draggable="false"
+      @error="emit('error')"
     />
 
     <!-- Zoom hint -->

src/components/MediaStage.vue

@@ -82,6 +82,7 @@ defineExpose({
           :item="item"
           :presentation="presentation"
           class="media-stage__viewer"
+          @error="error = true; url = ''"
         />
       </template>
       <template #fallback>