feat: add Scan New button to OCR matched-assets result view

When OCR detects serial numbers matching assets in the DB but no
machine_id pattern (XXXXX-XXXXXX) is found, the result now shows:
- 'Asset found via serial/ID match' heading
- Matched assets with name, serial_number, machine_id, matched_on
- View Details button per matched asset
- Scan New + Retake buttons at the bottom

When machine_id IS found AND matched_assets also has entries, the
matched assets are shown as supplementary info below the main result.

The OCR vision prompt already asked for 'serial numbers' (no change
needed on server side).

static/index.html

@@ -3427,7 +3427,10 @@
           <div style="font-size:16px;font-weight:600;color:var(--green);">✅ Asset found via serial/ID match</div>
           ${data.raw_text ? `<div class="or-raw">OCR text: ${esc(data.raw_text)}</div>` : ''}
           ${matchedHtml}
-          <div style="margin-top:8px;"><button class="btn btn-outline btn-sm" onclick="retakeOcr()" style="width:100%;">🔄 Retake</button></div>`;
+          <div style="margin-top:8px;display:flex;gap:6px;">
+            <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/ID match!', 'success');
       } else {
         el.innerHTML = `