GHSA-4xgf-cpjx-pc3j: pydantic-settings: NestedSecretsSettingsSource follows symlinks outside secrets_dir, enabling local file read and bypassing secrets_dir_max_size

A vulnerability in pydantic-settings' `NestedSecretsSettingsSource` (a feature that reads secret values from files in a directory) allows attackers to read files outside the configured secrets directory by creating symbolic links (shortcuts that point to other locations on the system). The same flaw also bypasses `secrets_dir_max_size`, a size limit meant to prevent loading excessively large files. This can happen when `secrets_nested_subdir=True` is enabled and an attacker can add symbolic links to the secrets directory.