feat(admin): add document preview functionality to adult verification

- Implemented a preview section for adult verification documents, allowing users to view images and PDFs inline.
- Added localization support for preview titles and messages in German, English, and Spanish.
- Enhanced the component's state management to handle preview visibility and cleanup.

frontend/src/i18n/locales/de/admin.json

@@ -42,6 +42,9 @@
             "reject": "Ablehnen",
             "resetPending": "Auf Prüfung setzen",
             "openDocument": "Dokument ansehen",
+            "previewTitle": "Nachweis-Vorschau",
+            "closePreview": "Vorschau schließen",
+            "previewUnavailable": "Für diesen Dateityp ist hier keine Vorschau verfügbar.",
             "empty": "Keine passenden Anfragen gefunden.",
             "loadError": "Die Freigaben konnten nicht geladen werden.",
             "updateError": "Der Status konnte nicht geändert werden.",

frontend/src/i18n/locales/en/admin.json

@@ -42,6 +42,9 @@
             "reject": "Reject",
             "resetPending": "Set pending",
             "openDocument": "Open document",
+            "previewTitle": "Proof preview",
+            "closePreview": "Close preview",
+            "previewUnavailable": "No inline preview is available for this file type.",
             "empty": "No matching requests found.",
             "loadError": "Could not load approvals.",
             "updateError": "Could not update the status.",

frontend/src/i18n/locales/es/admin.json

@@ -42,6 +42,9 @@
             "reject": "Rechazar",
             "resetPending": "Poner en revisión",
             "openDocument": "Abrir documento",
+            "previewTitle": "Vista previa de la prueba",
+            "closePreview": "Cerrar vista previa",
+            "previewUnavailable": "No hay vista previa integrada para este tipo de archivo.",
             "empty": "No se han encontrado solicitudes.",
             "loadError": "No se pudieron cargar las aprobaciones.",
             "updateError": "No se pudo actualizar el estado.",

frontend/src/views/admin/AdultVerificationView.vue

@@ -66,6 +66,24 @@
         </tbody>
       </table>
     </section>
+
+    <section v-if="previewUrl" class="adult-verification__preview surface-card">
+      <div class="adult-verification__preview-header">
+        <div>
+          <strong>{{ $t('admin.adultVerification.previewTitle') }}</strong>
+          <span v-if="previewRow">{{ previewRow.username }} · {{ previewRow.adultVerificationRequest?.originalName }}</span>
+        </div>
+        <button type="button" class="secondary" @click="clearPreview">
+          {{ $t('admin.adultVerification.closePreview') }}
+        </button>
+      </div>
+
+      <img v-if="isImagePreview" :src="previewUrl" class="adult-verification__preview-image" />
+      <iframe v-else-if="isPdfPreview" :src="previewUrl" class="adult-verification__preview-pdf" />
+      <div v-else class="adult-verification__state">
+        {{ $t('admin.adultVerification.previewUnavailable') }}
+      </div>
+    </section>
   </div>
 </template>
 
@@ -79,7 +97,10 @@ export default {
     return {
       loading: false,
       statusFilter: 'pending',
-      rows: []
+      rows: [],
+      previewUrl: '',
+      previewMimeType: '',
+      previewRow: null
     };
   },
   computed: {
@@ -90,6 +111,12 @@ export default {
         { value: 'rejected', label: this.$t('admin.adultVerification.filters.rejected') },
         { value: 'all', label: this.$t('admin.adultVerification.filters.all') }
       ];
+    },
+    isImagePreview() {
+      return this.previewMimeType.startsWith('image/');
+    },
+    isPdfPreview() {
+      return this.previewMimeType === 'application/pdf';
     }
   },
   methods: {
@@ -109,6 +136,7 @@ export default {
     },
     async changeFilter(filter) {
       this.statusFilter = filter;
+      this.clearPreview();
       await this.load();
     },
     async setStatus(row, status) {
@@ -125,16 +153,28 @@ export default {
         const response = await apiClient.get(`/api/admin/users/${row.id}/adult-verification/document`, {
           responseType: 'blob'
         });
-        const url = window.URL.createObjectURL(response.data);
+        this.clearPreview();
-        window.open(url, '_blank', 'noopener');
+        this.previewMimeType = response.data.type || '';
-        window.setTimeout(() => window.URL.revokeObjectURL(url), 10000);
+        this.previewUrl = window.URL.createObjectURL(response.data);
+        this.previewRow = row;
       } catch (error) {
         showApiError(this, error, this.$t('admin.adultVerification.documentError'));
       }
+    },
+    clearPreview() {
+      if (this.previewUrl) {
+        window.URL.revokeObjectURL(this.previewUrl);
+      }
+      this.previewUrl = '';
+      this.previewMimeType = '';
+      this.previewRow = null;
     }
   },
   async mounted() {
     await this.load();
+  },
+  beforeUnmount() {
+    this.clearPreview();
   }
 };
 </script>
@@ -147,7 +187,8 @@ export default {
 
 .adult-verification__hero,
 .adult-verification__filters,
-.adult-verification__list {
+.adult-verification__list,
+.adult-verification__preview {
   background: linear-gradient(180deg, rgba(255, 252, 247, 0.97), rgba(250, 244, 235, 0.95));
   border: 1px solid var(--color-border);
   border-radius: var(--radius-lg);
@@ -232,10 +273,41 @@ export default {
   background: transparent;
 }
 
+.adult-verification__preview-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  margin-bottom: 14px;
+}
+
+.adult-verification__preview-header > div {
+  display: grid;
+  gap: 4px;
+}
+
+.adult-verification__preview-image,
+.adult-verification__preview-pdf {
+  width: 100%;
+  border-radius: var(--radius-md);
+  border: 1px solid rgba(93, 64, 55, 0.08);
+  background: rgba(255, 255, 255, 0.78);
+}
+
+.adult-verification__preview-image {
+  max-height: 70vh;
+  object-fit: contain;
+}
+
+.adult-verification__preview-pdf {
+  min-height: 70vh;
+}
+
 @media (max-width: 760px) {
   .adult-verification__hero,
   .adult-verification__filters,
-  .adult-verification__list {
+  .adult-verification__list,
+  .adult-verification__preview {
     padding: 18px;
   }