Enable Mamba as Summary Nets

[stefanradev93]

Wraps Mamba State Space Model (SSM) as a powerful summary network for time series. Usage:

summary_net = MambaSSM()

Credit to: https://github.com/state-spaces/mamba/tree/main

Note: Only supports torch backend due to hardware-aware optimization.

[codecov]

Codecov Report

Attention: Patch coverage is 59.42029% with 28 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
bayesflow/wrappers/mamba/mamba.py	57.57%	14 Missing ⚠️
bayesflow/wrappers/mamba/mamba_block.py	58.82%	14 Missing ⚠️

Files with missing lines	Coverage Δ
bayesflow/wrappers/__init__.py	100.00% <100.00%> (ø)
bayesflow/wrappers/mamba/__init__.py	100.00% <100.00%> (ø)
bayesflow/wrappers/mamba/mamba.py	57.57% <57.57%> (ø)
bayesflow/wrappers/mamba/mamba_block.py	58.82% <58.82%> (ø)

... and 11 files with indirect coverage changes

[LarsKue]

Looks good overall. I would change some minor things, see individual comments.