migrator: update Sonarr/Whisparr RelativePath tables during root-folder migration

[nicholaskurjo]

Summary

• add Sonarr/Whisparr migration coverage for:
  • EpisodeFiles.RelativePath
  • MetadataFiles.RelativePath
  • SubtitleFiles.RelativePath
• keep existing absolute-path behavior for Path columns
• add targeted RelativePath rewrite logic to normalize path separators when migrating between Windows and Linux style roots

Why

Issue #214 reports that root-folder migration alone leaves additional Sonarr tables with mismatched separator styles in RelativePath, causing re-scan churn and related DB/log issues after cross-OS migration.

Implementation

• updated AppTables("Sonarr") and AppTables("Whisparr") in pkg/starrs/migrator.go to include the three RelativePath tables
• introduced rewritePathForTable(...):
  • Path columns: prefix replace (existing behavior)
  • RelativePath columns: separator normalization based on old/new root style
• updateFilesRootFolder(...) now routes updates through this helper

Tests

Added pkg/starrs/migrator_test.go with coverage for:

• existing Path rewrite behavior
• RelativePath rewrite Win -> Linux
• RelativePath rewrite Linux -> Win
• Sonarr/Whisparr table map includes the new RelativePath tables

Ran:

• go test ./pkg/starrs
• go test ./... (with temporary local frontend/dist placeholder for embed during test run)

Closes #214