fix(sales-invoice): force-unhide Tax Articles grid column across sites

create_custom_fields() applies only the properties present in each field
def (cf.update(df)). The custom_tax_articles_display def listed
in_list_view=1 but omitted 'hidden', so a site where the field had
hidden=1 would never converge on migrate -> the column showed on one
machine and stayed hidden on another. Make hidden=0 explicit so migrate
force-applies it everywhere.

Verified: forcing hidden=1 then running create_custom_fields() now resets
it to hidden=0.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

jey_erp/custom_fields.py

@@ -932,6 +932,7 @@ def create_custom_fields():
                 insert_after='custom_si_row_key',
                 read_only=1,
                 in_list_view=1,
+                hidden=0,
                 columns=2,
                 description='Click to select tax articles'
             )