Bundle exactly PR #6 (df4eb9b) as the diffusers source

Move bnb Params4bit.shape fix to a runtime shim in app.py; restore pristine bundled diffusers

Fix bnb Params4bit.shape tuple (.numel via math.prod); unpin bitsandbytes for cu130

Bundle PR diffusers (yiyi-refactor-fused + native prompt upsampling)

bnb: math.prod(shape) so tuple works

Embed diffusers PR source; install locally