🐛 Fix model_fields_optional compatibility with pydantic 2.11.x and linting

- Use `copy.copy()` fallback for FieldInfo when `_copy()` is unavailable
  (added in pydantic 2.12.0, but project supports >=2.11.0)
- Replace `Union[X, None]` with `X | None` to satisfy ruff UP007/UP045
- Apply ruff formatting fixes

Author: Krishnachaitanyakc

sqlmodel/main.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import builtins
+import copy
 import ipaddress
 import uuid
 import weakref
@@ -594,15 +595,18 @@ def __new__(
                         ann = field_info.annotation
                         # Only wrap in Optional if not already Optional
                         if ann is not None and not _is_optional_annotation(ann):
-                            pydantic_annotations[field_name] = Union[ann, None]
+                            pydantic_annotations[field_name] = ann | None
                         else:
                             pydantic_annotations[field_name] = ann
                         # Set default to None if the field was required and
                         # not already defined in the current class
                         if field_name not in dict_for_pydantic:
                             # Copy the FieldInfo to preserve metadata like
                             # min_length, ge, etc.
-                            new_field_info = field_info._copy()
+                            if hasattr(field_info, "_copy"):
+                                new_field_info = field_info._copy()
+                            else:
+                                new_field_info = copy.copy(field_info)
                             if new_field_info.is_required():
                                 new_field_info.default = None
                             dict_for_pydantic[field_name] = new_field_info