fix: decouple barcode detection from OCR engines
Summary
Decouples barcode detection from the selected OCR engine so that barcode processing behaves consistently with Tesseract and Paddle OCR profiles.
Changes
- introduces a dedicated barcode service;
- removes barcode detection dependency from OCR engine selection;
- updates document processing integration;
- adds regression tests;
- adds technical documentation.
Validation
- targeted barcode suite: 20 passed, 2 known warnings;
- correlated OCR/hOCR regression suite: 67 passed, 2 known warnings;
- tracked full suite: 90 passed, 11 skipped, 14 pre-existing quality-endpoint fixture errors;
- no new failures or collection errors in tracked tests;
- branch and remote tracking reference are aligned;
- whitespace check passed;
- tracked working tree and index are clean.
Scope
This merge request does not contain the subsequent hOCR bounding-box integrity correction.