[WIP] Fix incorrect category display in report for same merchant names

[Copilot]

• Fix analyze_transactions to use (merchant, category, subcategory) composite key in by_merchant, store name in data dict
• Update classify_by_sections to use data.get('name', '') instead of tuple key for merchant name
• Update export_json, export_markdown, export_csv, print_summary in analyzer.py to use data.get('name', '') for display
• Update report.py build_section_merchants to use data.get('name', merchant_key) for display name and composite ID for uniqueness; update build_category_view
• Update explain.py to search by_merchant by data['name'] instead of dict key; update _print_classification_summary and _print_explain_summary
• Add tests for same-merchant-name-different-category behavior
• Run tests to validate fix

[terryaney]

@copilot What am I supposed to do next? The code looks ok. I want to test it, but you also threw a rate limiting exception so I'm not sure if you are done or not.