Wire metadata previews through ExifTool store with friendly status messages.

Prefetch ExifTool on upload mount and track pending/loading/ready per file for batch preview loads.

frontend/src/views/UploadView.vue

@@ -4,3 +4,16 @@
         <p class="mt-2 text-muted-foreground">Upload UI coming soon.</p>
     </main>
 </template>
+
+<script setup lang="ts">
+import { onBeforeMount } from 'vue';
+import { useExiftoolStore } from '@/stores/exiftool';
+
+const exiftoolStore = useExiftoolStore();
+
+const { initializeExiftool } = exiftoolStore;
+
+onBeforeMount(() => {
+    initializeExiftool();
+});
+</script>