Fix PaccMann integration

[tereshchuk1]

This PR fixes the PaccMann implementation originally submitted in #388 by @gretag04, adapting it to work within the drevalpy framework.

Bug fixes

• Removed top-level pytoda imports in paccmann_v2.py: import pytoda and from pytoda.smiles.transforms import AugmentTensor were imported at the top level but pytoda is not a drevalpy dependency. Imports are now lazy (inside the confidence=True branch only), using the bundled stub in PaccMann/pytoda/.
• Fixed SMILES loading
• Fixed gene list name

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 71.91011% with 125 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.11%. Comparing base (7d24cd6) to head (3c2a22f).
⚠️ Report is 54 commits behind head on development.

Files with missing lines	Patch %	Lines
drevalpy/models/PaccMann/utils/interpret.py	12.50%	63 Missing ⚠️
drevalpy/models/PaccMann/utils/loss_functions.py	20.83%	19 Missing ⚠️
drevalpy/models/PaccMann/paccmann_v2.py	85.10%	14 Missing ⚠️
drevalpy/models/PaccMann/utils/layers.py	74.07%	14 Missing ⚠️
drevalpy/models/PaccMann/paccmann.py	95.03%	8 Missing ⚠️
drevalpy/models/PaccMann/utils/utils.py	75.00%	7 Missing ⚠️
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Additional details and impacted files

@@               Coverage Diff               @@
##           development     #447      +/-   ##
===============================================
+ Coverage        80.34%   81.11%   +0.77%     
===============================================
  Files              101      127      +26     
  Lines             8171    10057    +1886     
===============================================
+ Hits              6565     8158    +1593     
- Misses            1606     1899     +293     

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