feat(bun): generate native Go array slices for PostgreSQL array columns

Bun's pgdialect scans/appends native slices directly, so array columns
(text[], integer[], uuid[], ...) always generate as plain []string,
[]int32, etc. with an explicit "array" bun tag, regardless of --types
(sqltypes/stdlib/baselib). The SqlXxxArray wrapper types are no longer
used for Bun array columns (gorm is unaffected and keeps using them).

Adds --array-nullable pointer_slice to represent nullable array columns
as *[]T instead of []T, so callers can distinguish SQL NULL (nil) from
'{}' (pointer to an empty slice). Verified end-to-end against a live
PostgreSQL instance for NULL/{}/populated arrays in every --types mode.

Closes #13

pkg/writers/bun/writer.go

@@ -24,7 +24,7 @@ type Writer struct {
 func NewWriter(options *writers.WriterOptions) *Writer {
 	w := &Writer{
 		options:    options,
-		typeMapper: NewTypeMapper(options.NullableTypes),
+		typeMapper: NewTypeMapper(options.NullableTypes, options.NullableArrays),
 		config:     LoadMethodConfigFromMetadata(options.Metadata),
 	}