UUID autocomplete fails due to wrong field mapping access

[MrNancy]

When submitting an autocomplete field that uses a UUID as the entity identifier, EasyAdmin throws an error because the Doctrine field mapping is accessed as an object ($idFieldMapping->type).
However, getFieldMapping() returns an array, not an object.

This causes the UUID type check to fail, preventing correct binary conversion and breaking autocomplete submissions for UUID-based entities.

To Reproduce

1. Use an entity where the primary key is a UUID field mapped with uuid_binary (Doctrine UuidType).
2. Configure an autocomplete field in EasyAdmin referencing this entity.
3. Submit the form with a selected autocomplete value.
4. EasyAdmin triggers an error similar to:
5. Attempt to read property "type" on array

    /**
     * Gets the mapping of a (regular) field that holds some data but not a
     * reference to another object.
     *
     * @param string $fieldName The field name.
     *
     * @return mixed[] The field mapping.
     * @phpstan-return FieldMapping
     *
     * @throws MappingException
     */
    public function getFieldMapping($fieldName)
    {
        if (! isset($this->fieldMappings[$fieldName])) {
            throw MappingException::mappingNotFound($this->name, $fieldName);
        }

        return $this->fieldMappings[$fieldName];
    }

Expected behavior

EasyAdmin should correctly detect the field type by accessing it as an array:

$idFieldMapping['type']

This allows the UUID to be converted properly:
Uuid::fromString($v)->toBinary();