Add payment line parser and fix OCR override from payment_line

- Add MachineCodeParser for Swedish invoice payment line parsing
- Fix OCR Reference extraction by normalizing account number spaces
- Add cross-validation tests for pipeline and field_extractor
- Update UI layout for compact upload and full-width results

Key changes:
- machine_code_parser.py: Handle spaces in Bankgiro numbers (e.g. "78 2 1 713")
- pipeline.py: OCR and Amount override from payment_line, BG/PG comparison only
- field_extractor.py: Improved invoice number normalization
- app.py: Responsive UI layout changes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/validation/__init__.py

@@ -0,0 +1,7 @@
+"""
+Cross-validation module for verifying field extraction using LLM.
+"""
+
+from .llm_validator import LLMValidator
+
+__all__ = ['LLMValidator']