feat: Add support for skipping processed files in transfer configs

- Introduce new `skip_processed_files` option for transfer configurations
- Add database migration to support the new column
- Update config form and UI to include skip processed files toggle
- Enhance scheduler to respect skip processed files setting
- Modify file processing logic to optionally skip previously processed files
- Add environment variable support for skip processed files configuration

.gitignore

@@ -58,6 +58,10 @@ components/providers/common/*.go
 # Ignore the data directory
 data/
 
+# Ignore .env files
+.env
+*.env
+
 # Ignore the tmp directory
 tmp/