ADD V2 API inference and mask decoding helpers

[Everloom-129]

Hi,

This PR adds two helper files to support the current V2 DDS Cloud API:

1. dinox_detector.py

   • Provides get_dinox() to call the /v2/task/dinox/detection endpoint with V2Task
   • Includes visualize_bbox_and_mask() using supervision library for fast local visualization

2. mask_utils.py

   • Decodes RLE-format masks to binary numpy arrays
   • Includes _string2rle() and _rle2mask() for compatibility with returned mask format

This may be useful for new users who want to experiment with DINO-X via Python SDK with up-to-date API.

Let me know if you’d like me to refactor these into your codebase structure. Thanks for the great work!

Best,
Jie Wang
GRASP Lab, UPenn