fix(bria_fibo): honor timesteps, fix edit num_images batching, add _no_split_modules, fix docstring

[akshan-main]

What does this PR do?

Part of #13618 (bria_fibo review), follow-up to #13981:

• BriaFiboEditPipeline crashed with num_images_per_prompt > 1: the encoded image latents kept the original image batch and weren't repeated to the prompt batch before packing. Now repeated.
• timesteps is accepted and documented but has never been used; passing it now raises a deprecation warning instead of silently doing nothing.
• The pipelines hardcoded vae_scale_factor = 16 instead of reading the VAE's scale_factor_spatial; now read from config.
• BriaFiboTransformer2DModel was missing _no_split_modules, so device_map/offload could split residual transformer blocks. Declared the two block classes the model uses (this also enables 4 previously-skipped sharding tests, which pass).
• The edit example docstring had a leftover # TODO and called the unimported ModularPipelineBlocks; switched to the imported ModularPipeline and removed the TODO.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline?
• Did you read our philosophy doc (important for complex PRs)?
• Was this discussed/approved via a GitHub issue or the forum? Discussed on Slack with @yiyixuxu
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Who can review?

@yiyixuxu @sayakpaul

[github-actions]

Hi @akshan-main, thanks for the PR! It does not appear to link an issue it fixes. If this PR addresses an existing issue, please add a closing keyword (e.g. Fixes #1234) to the PR description so the issue is linked. See the contribution guide for more details. If this PR intentionally does not fix a tracked issue, a maintainer can add the no-issue-needed label to silence this reminder.

[yiyixuxu]

thanks!

[yiyixuxu]

we talked about standardlize this across pipelines using a function like this https://github.com/huggingface/diffusers/blob/main/src/diffusers/pipelines/ideogram4/pipeline_ideogram4.py#L115

maybe we can start addingthat while you're doing these pipeline refactors?

[yiyixuxu]

we can just deprecate timesteps instead (it has not been used so far)

[yiyixuxu]

see example https://github.com/huggingface/diffusers/blob/main/src/diffusers/pipelines/stable_diffusion/pipeline_stable_diffusion.py#L896