Guard by_name kwarg for pydantic < 2.11

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### Summary

`polyfactory/factories/pydantic_factory.py:570` calls
`cls.__model__.model_validate(kwargs, by_name=True)` when `__by_name__` is set.

The `by_name` keyword argument was added to `model_validate` in pydantic 2.11.0.
On pydantic < 2.11 it raises

```
TypeError: BaseModel.model_validate() got an unexpected keyword argument 'by_name'
```

(verified on pydantic 2.10.6).

The project declares `pydantic[email]>=2.10.4`, which permits versions below
2.11, so the option can only be used on pydantic >= 2.11 in practice.

### Impact

- `TypeError` at factory build time on pydantic 2.10.4–2.10.x when a factory
sets `__by_name__ = True`.
- The declared minimum (2.10.4) does not actually support the feature.

### Suggested fix

Guard the `by_name` argument with a pydantic version check, keeping the
existing behavior on pydantic >= 2.11:

```python
if cls.__by_name__ and _is_pydantic_v2_model(cls.__model__):
if _PYDANTIC_HAS_BY_NAME: # pydantic >= 2.11
return cls.__model__.model_validate(kwargs, by_name=True)
return cls.__model__.model_validate(kwargs)
```

Alternatively, raise the minimum declared version to `pydantic>=2.11`.

Start at polyfactory/factories/pydantic_factory.py:570 and reproduce the failure with pydantic 2.10.6 when __by_name__ is enabled. Check the version compatibility around model_validate, then verify that pydantic below 2.11 omits by_name while 2.11 and newer retain the existing behavior.

Written by the indexing model from the issue text.