barcode scan: add confirmation step before auto check-in

- Existing assets now show a confirm card with machine ID + ✓ Confirm & Check In / ✏️ Edit buttons
- Confirm triggers auto check-in then shows the result card
- Edit opens inline machine ID editor with Re-lookup
- Cancel button returns to original confirmation
- New asset flow unchanged (form already editable)

static/index.html

@@ -3080,8 +3080,7 @@
 
       try {
         const asset = await api(`/api/assets/search?machine_id=${encodeURIComponent(machineId)}`);
-        autoCheckin(asset.id);
+        showScanConfirm(asset, machineId);
-        showScannedAsset(asset);
       } catch (e) {
         if (e.message === 'Asset not found' || e.message.includes('404')) {
           showNewAssetForm(machineId);
@@ -3112,6 +3111,78 @@
       `;
     }
 
+    function showScanConfirm(asset, machineId) {
+      AppState.currentAssetId = asset.id;
+      setScanStatus('Confirm machine ID', 'info');
+
+      const el = document.getElementById('scanResult');
+      el.style.display = 'block';
+      el.innerHTML = `
+        <div class="sr-name">${esc(asset.name)}</div>
+        <div class="sr-meta">
+          Machine ID: <strong>${esc(machineId)}</strong> · ${esc(asset.category || 'Other')} ·
+          <span class="status-tag ${asset.status}">${asset.status || 'active'}</span>
+        </div>
+        <div class="sr-actions" style="flex-wrap:wrap;">
+          <button class="btn btn-primary btn-sm" onclick="confirmScanCheckin(${asset.id})" style="flex:1;">✓ Confirm & Check In</button>
+          <button class="btn btn-outline btn-sm" onclick="showMachineIdEditor('${esc(machineId)}')">✏️ Edit</button>
+        </div>
+      `;
+    }
+
+    async function confirmScanCheckin(assetId) {
+      setScanStatus('Checking in...', 'working');
+      await autoCheckin(assetId);
+      const asset = await api(`/api/assets/${assetId}`);
+      showScannedAsset(asset);
+    }
+
+    function showMachineIdEditor(currentId) {
+      const el = document.getElementById('scanResult');
+      el.innerHTML = `
+        <div style="font-size:13px;color:var(--text2);margin-bottom:6px;">Edit machine ID:</div>
+        <div style="display:flex;gap:6px;">
+          <input type="text" id="editMachineIdInput" value="${esc(currentId)}"
+                 style="flex:1;border:1px solid var(--border);border-radius:6px;padding:8px;font-size:16px;background:var(--bg1);color:var(--text1);"
+                 onkeydown="if(event.key==='Enter')relookupMachineId()">
+          <button class="btn btn-primary btn-sm" onclick="relookupMachineId()">Re-lookup</button>
+        </div>
+        <div id="editMachineIdError" style="color:var(--err);font-size:12px;margin-top:4px;display:none;"></div>
+        <div style="margin-top:8px;">
+          <button class="btn btn-outline btn-sm" onclick="showScanConfirmFromEdit()">← Cancel</button>
+        </div>
+      `;
+      document.getElementById('editMachineIdInput').focus();
+      document.getElementById('editMachineIdInput').select();
+    }
+
+    async function relookupMachineId() {
+      const newId = document.getElementById('editMachineIdInput').value.trim();
+      if (!newId) return;
+      setScanStatus('Re-looking up...', 'working');
+      try {
+        const asset = await api(`/api/assets/search?machine_id=${encodeURIComponent(newId)}`);
+        showScanConfirm(asset, newId);
+      } catch (e) {
+        if (e.message === 'Asset not found' || e.message.includes('404')) {
+          showNewAssetForm(newId);
+        } else {
+          document.getElementById('editMachineIdError').textContent = 'Lookup error: ' + e.message;
+          document.getElementById('editMachineIdError').style.display = 'block';
+        }
+      }
+    }
+
+    function showScanConfirmFromEdit() {
+      const assetId = AppState.currentAssetId;
+      if (!assetId) return;
+      api(`/api/assets/${assetId}`).then(asset => {
+        showScanConfirm(asset, asset.machine_id);
+      }).catch(() => {
+        setScanStatus('Could not reload asset', 'error');
+      });
+    }
+
     function showNewAssetForm(machineId) {
       currentScannedMachineId = machineId;
       setScanStatus('Machine ID not in database — create asset below', 'error');