fix: Add missing transformers dependency for nano-graphrag

- Add transformers>=4.0.0 to requirements.txt
- Required for nano-graphrag imports to work properly

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Co-Authored-By: Claude <noreply@anthropic.com>

requirements.txt

@@ -13,4 +13,5 @@ nano-vectordb>=0.0.4
 dspy-ai>=3.0.0
 neo4j>=5.0.0
 graspologic
-aioboto3
+aioboto3
+transformers>=4.0.0