WooCommerce PDF Invoices

## What's New
- Extended Packaging Slips Integration: Added native support for including item variation images directly on packaging slips and picking lists.
- Dynamic Sequential Invoicing: Improved database locking mechanisms during high-concurrency checkout traffic to guarantee perfect invoice number sequencing without gaps.

## Bug Fixes
- RTL Layout Alignment: Fixed a PDF rendering bug where right-to-left (RTL) languages like Arabic and Hebrew caused table structures and currency symbols to overlap.
- Tax Split Display Error: Resolved an issue where multiple tax classes (e.g., compound or reduced rates) were summing incorrectly inside the total invoice footer breakdown.
- Dompdf Memory Spike: Optimized temporary file cleanup routines within the PDF generator engine to mitigate PHP memory limit exhausted crashes during bulk generation.