Implement issue 1 search, order reuse and tracking

po_app/static/search_select.js

@@ -0,0 +1,16 @@
+/* Filter existing supplier/material options without changing their submitted IDs. */
+window.POFilterSelect = {
+  bind: function (input, select) {
+    if (!input || !select) return;
+    const options = Array.from(select.options);
+    const normalize = value => String(value || '').trim().toLocaleLowerCase();
+    input.addEventListener('input', function () {
+      const term = normalize(input.value);
+      const matches = options.filter((option, index) => index === 0 ||
+        normalize(option.textContent + ' ' + (option.dataset.search || '')).includes(term));
+      select.replaceChildren(...matches);
+      select.selectedIndex = 0;
+      select.setAttribute('aria-label', term ? `匹配 ${matches.length - 1} 项，请选择` : '请选择');
+    });
+  }
+};