feat: Add dataset and job management

- Introduced dataset management functionalities in a new dataset_manager.py file, including dataset creation, validation, and video scene splitting.
- Added job management system with a new job database and worker scripts for processing training jobs.
- Implemented a command-line interface for training that integrates with the job queue system.
- Created a script to start both the Gradio UI and the queue worker simultaneously.

Author: fengtricks

.gitignore

@@ -26,4 +26,7 @@ configs/*.yaml
 !configs/ltxv_2b_full.yaml
 !configs/ltxv_2b_lora.yaml
 !configs/ltxv_2b_lora_low_vram.yaml
-outputs
+outputs/
+datasets/
+training_data/
+*.db