Fix all TS6133 errors (unused variables) across service layer:
- Remove unused imports (path, ExtractionProgress type)
- Prefix unused parameters with underscore (_session, _totalBatches, etc.)
- Remove unused _verbose field and constructor from ExcelParser
- Remove unused _importToDatabase method from ExtractorService
- Remove unused _importProgress variable
This ensures clean type checking and eliminates dead code.
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>