Unit tests:
- series_service_test.go: test continueSeriesRowToMediaItems conversion
with valid fields, null fields, and comprehensive field mapping
- series_test.go: test handler initialization and textToString helper
Integration tests (series_integration_test.go):
- GET /api/series: requires library_id, rejects invalid UUID, returns
empty array for empty library, pagination params, limit clamped to
100, response structure validation, special characters in names
- GET /api/series/books: requires library_id and name, handles
nonexistent series, unauthorized access
- Restore Continue Series system collection
- Dashboard sections include all 5 collections (including continue-series)
Update test helpers:
- Add SeriesHandler to setupTestServer router config
- Add 5th Continue Series collection to createDefaultCollectionsForUser
- Update dashboard integration test for 5 collections
