fix: auto-inject JasperReports namespace before XSD validation

AI-generated JRXML often omits the xmlns declaration on the root element.
The XSD schema requires targetNamespace, so validation would fail with
"Element 'jasperReport': No matching global declaration available".

_ensure_jr_namespace() detects missing xmlns and injects it before
schema validation, making the validator tolerant of namespace-free JRXML.

validation_service/main.py

@@ -111,11 +111,28 @@ def _check_minimum_content(jrxml: str) -> list[str]:
     return issues
 
 
+JR_NAMESPACE = "http://jasperreports.sourceforge.net/jasperreports"
+
+
+def _ensure_jr_namespace(jrxml: str) -> str:
+    """如果 JRXML 根元素缺少命名空间声明，自动补上。"""
+    import re
+    if 'xmlns=' not in jrxml[:500]:
+        return re.sub(
+            r'(<jasperReport)\b',
+            r'\1 xmlns="' + JR_NAMESPACE + '"',
+            jrxml, count=1,
+        )
+    return jrxml
+
+
 def _validate_xsd(jrxml: str) -> tuple[bool, str]:
     """根据 JasperReports XSD schema 验证 JRXML。"""
     if not SCHEMA_FILE.exists():
         return True, ""
 
+    jrxml = _ensure_jr_namespace(jrxml)
+
     try:
         schema_doc = etree.parse(str(SCHEMA_FILE))
         xmlschema = etree.XMLSchema(schema_doc)