refactor(db): simplify migration functions by removing dead counting logic (#934)

The migrateRecordings, migrateTransformations, and migrateTransformationRuns functions tracked migratedCount, skippedCount, and errorCount variables, but these counts were never used anywhere in the codebase. All callsites only check the error status, never the returned counts.

Removed:
- Three count variables from each function
- All increment operations (10 lines)
- Progress logging with counts
- Return objects with count data

The migration behavior is identical. Kept all essential logging and error handling. This makes the code 47 lines simpler while maintaining full functionality.

Author: braden-w