Make external VQA handlers (moondream3, joytag, joycaption, deepseek)
compatible with VQA load/unload mechanism for consistent model lifecycle.
- Added vqa_detection.py, add shared detection helpers
- Add load and unload functions to all external handlers
- Replace device_map="auto" with sd_models.move_model in joycaption
- Update dispatcher and moondream handlers to use shared helpers
