fix(api): emit canonical field-error items in timetable and pku_account envelopes

Validation errors now carry errors: {field: [{code, message}]}, the shape of the platform-wide envelope introduced by api/exceptions.py (PR #1014) and parsed by the mini-program's unified RequestError (YPPF-mini #10). Switching these modules to StandardizedExceptionHandlerMixin is a mechanical follow-up once #1014 lands.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012t4BD5H1P5nn2zF7oU6q9e

Author: tangmc0210

api/pku_account/views.py

@@ -112,12 +112,25 @@ def _first_message(errors: Any) -> str:
     return str(errors)
 
 
+def _field_errors(errors: Any) -> dict[str, list[dict[str, str]]]:
+    # Canonical ``{field: [{code, message}]}`` shape shared with api/exceptions.py.
+    if not isinstance(errors, dict):
+        return {}
+    result: dict[str, list[dict[str, str]]] = {}
+    for name, value in errors.items():
+        values = value if isinstance(value, (list, tuple)) else [value]
+        result[str(name)] = [
+            {'code': str(getattr(item, 'code', None) or 'invalid'), 'message': str(item)}
+            for item in values]
+    return result
+
+
 def _invalid(errors: Any) -> Response:
     return Response(
         {
             'code': 'INVALID_INPUT',
             'message': _first_message(errors),
-            'errors': errors,
+            'errors': _field_errors(errors),
         },
         status=status.HTTP_400_BAD_REQUEST,
     )

api/timetable/views.py

@@ -102,15 +102,19 @@ def _first_error(detail) -> str:
     return str(detail)
 
 
-def _field_errors(detail) -> dict[str, list[str]]:
+def _field_errors(detail) -> dict[str, list[dict[str, str]]]:
+    """Canonical field errors: ``{field: [{code, message}]}`` (same shape as
+    the platform-wide envelope of ``api/exceptions.py``)."""
     if not isinstance(detail, dict):
         return {}
-    errors: dict[str, list[str]] = {}
+    errors: dict[str, list[dict[str, str]]] = {}
     for name, value in detail.items():
         if name == 'detail':
             continue
         values = value if isinstance(value, (list, tuple)) else [value]
-        errors[str(name)] = [str(item) for item in values]
+        errors[str(name)] = [
+            {'code': str(getattr(item, 'code', None) or 'invalid'), 'message': str(item)}
+            for item in values]
     return errors