fix(bedrock): pass aws_profile to boto3.Session in _infer_region

[Vitaliy-Pikalo]

Fixes #892

Problem

_infer_region() creates a boto3.Session() without forwarding the aws_profile that was passed to the AnthropicBedrock / AsyncAnthropicBedrock constructor. This means the region is resolved from the default AWS profile, not the requested one — causing a 403 when the profile's region differs from the default.

Example: if aws_profile='prod' maps to us-west-2 in ~/.aws/config, the SDK still defaults to us-east-1 because boto3.Session() ignores the profile name.

Fix

Accept an optional aws_profile: str | None = None parameter in _infer_region() and pass it to boto3.Session(profile_name=aws_profile). Both AnthropicBedrock.__init__ and AsyncAnthropicBedrock.__init__ now forward aws_profile to the helper.

-def _infer_region() -> str:
+def _infer_region(aws_profile: str | None = None) -> str:
     ...
-            session = boto3.Session()
+            session = boto3.Session(profile_name=aws_profile)
     ...
-        self.aws_region = _infer_region() if aws_region is None else aws_region
+        self.aws_region = _infer_region(aws_profile) if aws_region is None else aws_region

When aws_profile is None (the default), boto3.Session(profile_name=None) behaves identically to boto3.Session(), so there is no change for existing callers that don't use a profile.