fix(TemplateManage): Ctrl+Z undo and smart-field insertion layout

- Intercept Ctrl+Z/Y keyboard shortcuts in keydown listener and route
to custom undoStack/redoStack to fix undo inconsistency.
- Replace execCommand('insertHTML') with precise Range.insertNode()
in insertSmartField to prevent <span> escaping out of <p> when
preceded by <br>.

src/pages/TemplateManage.tsx

@@ -186,6 +186,20 @@ export default function TemplateManage() {
     if (!editor) return;
 
     const handleKeyDown = (e: KeyboardEvent) => {
+      if ((e.ctrlKey || e.metaKey) && e.key.toLowerCase() === 'z') {
+        e.preventDefault();
+        if (e.shiftKey) {
+          handleRedo();
+        } else {
+          handleUndo();
+        }
+        return;
+      }
+      if ((e.ctrlKey || e.metaKey) && e.key.toLowerCase() === 'y') {
+        e.preventDefault();
+        handleRedo();
+        return;
+      }
       if (e.key !== 'Backspace' && e.key !== 'Delete') return;
       const sel = window.getSelection();
       if (!sel || !sel.isCollapsed || sel.rangeCount === 0) return;
@@ -310,8 +324,31 @@ export default function TemplateManage() {
     }
     pushHistory();
     const html = `<span class="smart-field-wrapper" contenteditable="false" style="white-space:nowrap;position:relative;"><span class="field-value" data-bind="${field.key}" contenteditable="true" style="min-width:32px;padding:0 4px;margin:0 2px;border:1px solid #cbd5e1;border-radius:2px;display:inline-block;background:#f8fafc;color:#0f172a;line-height:1.2;font-size:inherit;vertical-align:text-bottom;box-sizing:border-box;min-height:1.2em;outline:none;"> </span><span class="delete-btn" contenteditable="false">×</span></span>&#8203;`;
-    document.execCommand('insertHTML', false, html);
+
+    const sel = window.getSelection();
+    if (sel && sel.rangeCount > 0) {
+      const range = sel.getRangeAt(0);
+      range.deleteContents();
+      const wrapper = document.createElement('div');
+      wrapper.innerHTML = html;
+      const fragment = document.createDocumentFragment();
+      while (wrapper.firstChild) {
+        fragment.appendChild(wrapper.firstChild);
+      }
+      range.insertNode(fragment);
+
+      const lastNode = fragment.lastChild;
+      if (lastNode) {
+        const newRange = document.createRange();
+        newRange.setStartAfter(lastNode);
+        newRange.collapse(true);
+        sel.removeAllRanges();
+        sel.addRange(newRange);
+      }
+    }
+
     editorRef.current?.focus();
+    saveTemplateContent();
   };
 
   const highlightField = (key: string, active: boolean) => {