Fix: pin huggingface_hub<0.29.0 to restore gradio compatibility

huggingface_hub 0.29.0 removed the deprecated HfFolder class.
gradio 4.44.1 still imports HfFolder via gradio.oauth, causing:
ImportError: cannot import name 'HfFolder' from 'huggingface_hub'

The unbounded `>=0.17.0` constraint let the Space install 0.29+.
Pinning to <0.29.0 restores compatibility without requiring a
major gradio upgrade to 5.x.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

requirements.txt

@@ -72,7 +72,8 @@ tqdm>=4.65.0
 # ============================================
 
 # For model downloading
-huggingface_hub>=0.17.0
+# Upper bound: huggingface_hub 0.29.0 removed HfFolder which gradio 4.x still imports
+huggingface_hub>=0.17.0,<0.29.0
 
 # Qwen2-VL specific utilities
 qwen-vl-utils>=0.0.2