Replace traditional OCR pipeline (table_detector, table_parser,
maintenance_patterns) with GeminiEngine for semantic PDF extraction.
Map Gemini serviceName values to 27 maintenance subtypes via
ServiceMapper fuzzy matching. Add 8 unit tests covering normal
extraction, unusual names, empty response, and error handling.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
