z-image support npu

[luren55]

What does this PR do?

Issue: The Diffusers Z-Image pipeline fails on Ascend NPU because aclnnIndex lacks support for complex64. When freqs_cis is stored as a complex tensor on the NPU and then indexed, the call crashes.

Fix: Rework the RoPE frequency handling so that the NPU never needs to index complex64 tensors.

Running Environment:
I run this model base on cache-dit(https://github.com/vipshop/cache-dit/) which depends on diffusers to inference.

Command:
python3 generate.py zimage --model-path /home/weights/Z-Image-Turbo --attn _native_npu

Error before fixed:

Result after fixed:

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[luren55]

@yiyuxuxu Hello, could you please review this pr, thank you.

[luren55]

@yiyixuxu @sayakpaul Hello, could you please review this pr, thank you.