Replace customer_list.js with customer_statements.js (loaded globally),
which adds the statement UI to both entry points:
- Customer list: 'Generate Statements' multi-select action.
- Customer form: 'Generate Statement' button for a single customer.
Both open a popup with a 'Generate late payment fee' checkbox (default on)
that maps to generate_statements(skip_late_fee), so fee billing can be
turned off per run. Shared generate/print helpers live on ns_statements.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>