feat(llm): add Amazon Bedrock as a first-class provider

Bedrock uses the Converse API (langchain-aws) and the AWS credential chain, so
it has its own client like Anthropic/Google rather than the OpenAI-compatible
registry. langchain-aws is an optional dependency (pip install ".[bedrock]"),
lazy-imported with a clear install hint; importing the package never requires
it. The model name is a Bedrock model ID / inference profile ID.

tradingagents/llm_clients/factory.py

@@ -43,6 +43,10 @@ def create_llm_client(
         from .azure_client import AzureOpenAIClient
         return AzureOpenAIClient(model, base_url, **kwargs)
 
+    if provider_lower == "bedrock":
+        from .bedrock_client import BedrockClient
+        return BedrockClient(model, base_url, **kwargs)
+
     from .openai_client import OpenAIClient, is_openai_compatible
     if is_openai_compatible(provider_lower):
         return OpenAIClient(model, base_url, provider=provider_lower, **kwargs)