Hotfix: Update rembg model string from bria to bria-rmbg for correct session mapping

Fix: Shift Bria RMBG execution to rembg ONNX runtime to resolve transformers package conflict entirely

Fix: HF Space 503 Startup Crash - downgrade transformers to 4.38.2 to fix RMBG tied weights bug

Fix: Pivot to briaai/RMBG-1.4 for reliable graphic alpha-matting instead of SAM

Hotfix: Update Dockerfile to bake transformers SAM weights

Fix: Implement facebook/sam-vit-base to guarantee correct mask resolution alignment

Fix: Replace rembg with Ultralytics MobileSAM for mathematically perfect vector masking

Major Quality Update: Switch to rembg U-2-Net with severe alpha matting, new crisp upscale logic

Quality: auto-detect BG color, stronger AA (7x7 Gaussian), morphological edge refinement, tolerance 45

Fix: cap upscale to 2048px max to prevent payload hang

Fix: box_threshold -> threshold for newer transformers API

Fix: replace deprecated libgl1-mesa-glx with libgl1

Fix: use valid HF color values

Fix: add HF Space YAML frontmatter for Docker SDK

Initial: FastAPI + Grounding DINO asset extraction API