fix: address thread-safety issues in framework integrations

- Replace shared _step_stack with parent_run_id approach in LangChain
- Use proper locking and parent-child relationships from framework callbacks
- Replace time.time() with UUID for unique IDs in LlamaIndex
- Remove unused _context_to_step tracking in Semantic Kernel
- Maintain thread-safe access patterns for concurrent executions

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: github-actions[bot]

src/praisonaiui/integrations/__init__.py

@@ -12,25 +12,28 @@
 def __getattr__(name: str):
     """Lazy import for framework integrations."""
     if name in ("AiuiLangChainCallbackHandler", "AsyncAiuiLangChainCallbackHandler"):
-        from praisonaiui.integrations.langchain import AiuiLangChainCallbackHandler, AsyncAiuiLangChainCallbackHandler
+        from praisonaiui.integrations.langchain import (
+            AiuiLangChainCallbackHandler,
+            AsyncAiuiLangChainCallbackHandler,
+        )
         if name == "AiuiLangChainCallbackHandler":
             return AiuiLangChainCallbackHandler
         else:
             return AsyncAiuiLangChainCallbackHandler
-    
+
     elif name == "AiuiLlamaIndexCallbackHandler":
         from praisonaiui.integrations.llama_index import AiuiLlamaIndexCallbackHandler
         return AiuiLlamaIndexCallbackHandler
-    
+
     elif name == "AiuiSemanticKernelFilter":
         from praisonaiui.integrations.semantic_kernel import AiuiSemanticKernelFilter
         return AiuiSemanticKernelFilter
-    
+
     raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
 
 __all__ = [
     "AiuiLangChainCallbackHandler",
-    "AsyncAiuiLangChainCallbackHandler", 
+    "AsyncAiuiLangChainCallbackHandler",
     "AiuiLlamaIndexCallbackHandler",
     "AiuiSemanticKernelFilter",
-]
+]