docs: update scan settings documentation for new polling system

- Update validation from minutes (15-1440) to seconds (1-3600)
- Clarify behavior: real-time file watching with polling fallback
- Remove scheduler references from development docs
- Update migration notes for the new implementation

docs/contributing/development.md

@@ -66,9 +66,8 @@ bookhoard/
 **Services** (`internal/services/`):
 
 - `library_service.go` - Library operations
-- `media_scanner.go` - File scanning & metadata extraction
+- `media_scanner.go` - File scanning, metadata extraction, and real-time file watching
 - `worker.go` - Job queue worker pool
-- `scheduler.go` - Scheduled task manager
 - `collection_service.go` - Collection rules processing
 - `conversion_service.go` - EPUB→KEPUB conversion
 - `book_matching.go` - Book matching algorithms