feat: local ZXing fallback, Register New Asset button, OCR serial search

Three fixes:
1. Barcode scanner: load ZXing locally with CDN fallback so it works
   even when CDN is unreachable.
2. Scan result: add 'Register' button to create a new asset from a
   scanned machine_id — works for both found and not-found results.
3. OCR serial search: when extracted machine_id isn't found, also try
   searching all numeric strings from OCR text as serial numbers; add
   'Register as New Asset' button on OCR not-found result.

static/index.html

@@ -4,7 +4,8 @@
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no, viewport-fit=cover">
   <title>Canteen Asset Tracker</title>
-  <script src="https://cdn.jsdelivr.net/npm/@zxing/library@0.20.0/umd/index.min.js"></script>
+  <!-- ZXing barcode scanner: local-first, CDN as fallback for offline/blocked networks -->
+  <script src="/zxing.min.js" onerror="this.remove();var s=document.createElement('script');s.src='https://cdn.jsdelivr.net/npm/@zxing/library@0.20.0/umd/index.min.js';document.head.appendChild(s)"></script>
   <script src="https://cdn.jsdelivr.net/npm/tesseract.js@5/dist/tesseract.min.js"></script>
   <!-- Leaflet Map -->
   <link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css" />
@@ -3144,6 +3145,7 @@
             ${hasGps ? '✓ GPS captured' : '📍 GPS needed'}
           </span>
           <button class="btn btn-outline btn-sm" onclick="switchTab('tabAssets');viewAsset(${asset.id});" style="flex:1;">View Details</button>
+          <button class="btn btn-outline btn-sm" onclick="registerNewAsset('${esc(asset.machine_id)}')" style="flex:1;">➕ Register</button>
           <button class="btn btn-primary btn-sm" onclick="resetBarcodeScanner()" style="flex:1;">Scan New</button>
         </div>
       `;
@@ -3238,10 +3240,32 @@
           Try OCR scanning the sticker, or search in the Assets tab.
         </div>
         <div style="margin-top:10px;">
+          <button class="btn btn-outline btn-sm" onclick="registerNewAsset('${esc(machineId)}')" style="width:100%;margin-bottom:6px;">➕ Register as New Asset</button>
           <button class="btn btn-primary btn-sm" onclick="resetBarcodeScanner()" style="width:100%;">Scan New</button>
         </div>`;
     }
 
+    // ── Register scanned barcode as a new asset ──────────────────────────
+    function registerNewAsset(machineId) {
+      const name = prompt('Enter a name for the new asset (machine_id: ' + machineId + '):');
+      if (!name) return;
+      api('/api/assets', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({
+          machine_id: machineId,
+          name: name,
+          category: 'other',
+          status: 'active',
+        }),
+      }).then(asset => {
+        showToast('✅ Asset created: ' + esc(asset.name), false);
+        showScannedAsset(asset);
+      }).catch(e => {
+        showToast('❌ Failed to create asset: ' + (e.message || e), true);
+      });
+    }
+
     function showCheckinForm() {
       document.getElementById('checkinNotes').value = '';
       document.getElementById('checkinCard').style.display = 'block';
@@ -3570,11 +3594,42 @@
       } catch (e) {
         if (e.message === 'Asset not found' || e.message.includes('404')) {
           const el = document.getElementById('ocrResult');
-          el.innerHTML = `
-            <div class="or-id">${esc(machineId)} ❌</div>
-            <div class="or-meta" style="color:var(--amber);">Machine ID not found in database</div>
-          <div style="margin-top:8px;"><button class="btn btn-outline btn-sm" onclick="retakeOcr()" style="width:100%;">🔄 Retake</button></div>`;
-          setOcrStatus('Asset not found — try scanning the barcode instead', 'error');
+          // Try to find by serial number from OCR raw_text
+          (async function searchOcrSerials() {
+            const rawText = document.querySelector('#ocrResult .or-raw');
+            if (rawText) {
+              const numbers = rawText.textContent.match(/\d{4,}/g);
+              if (numbers) {
+                for (const n of numbers.slice(0, 3)) {
+                  try {
+                    const bySerial = await api('/api/assets/search?machine_id=' + encodeURIComponent(n.trim()));
+                    if (bySerial) {
+                      const oci = categoryInfo(bySerial.category);
+                      el.innerHTML = `
+                        <div class="or-id">${esc(machineId)} ❌ → ${esc(bySerial.machine_id)} ✅</div>
+                        <div class="sr-name" style="font-size:16px;font-weight:700;margin:4px 0;"><span style="margin-right:6px">${oci.icon}</span>${esc(bySerial.name)}</div>
+                        <div class="or-meta">Found via serial: ${esc(n)} · ${esc(catLabel(bySerial.category))}</div>
+                        <div style="margin-top:8px;display:flex;gap:6px;">
+                          <button class="btn btn-outline btn-sm" onclick="switchTab('tabAssets');viewAsset(${bySerial.id});" style="flex:1;">View Details</button>
+                          <button class="btn btn-primary btn-sm" onclick="resetOcrScanner()" style="flex:1;">Scan New</button>
+                          <button class="btn btn-outline btn-sm" onclick="retakeOcr()" style="flex:1;">🔄 Retake</button>
+                        </div>`;
+                      setOcrStatus('Asset found via serial number!', 'success');
+                      AppState.currentAssetId = bySerial.id;
+                      return;
+                    }
+                  } catch (_) {}
+                }
+              }
+            }
+            // No serial match either — show not-found
+            el.innerHTML = `
+              <div class="or-id">${esc(machineId)} ❌</div>
+              <div class="or-meta" style="color:var(--amber);">Machine ID not found in database</div>
+            <div style="margin-top:8px;"><button class="btn btn-outline btn-sm" onclick="retakeOcr()" style="width:100%;">🔄 Retake</button>
+            <button class="btn btn-outline btn-sm" onclick="registerNewAsset('${esc(machineId)}')" style="width:100%;margin-top:4px;">➕ Register as New Asset</button></div>`;
+            setOcrStatus('Asset not found', 'error');
+          })();
         } else {
           setOcrStatus('Lookup error: ' + e.message, 'error');
         }