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

[nileshpatil6]

Problem

When a user passes aws_profile to AnthropicBedrock or AsyncAnthropicBedrock without an explicit aws_region, _infer_region() is called to look up the region. However _infer_region() creates boto3.Session() with no arguments, so the named profile's configured region is silently ignored. The client then falls back to AWS_REGION env var or hard-coded us-east-1.

Minimal reproduction:

# ~/.aws/config has [profile my-profile] with region = eu-west-1
client = AnthropicBedrock(aws_profile="my-profile")
print(client.aws_region)  # prints "us-east-1" instead of "eu-west-1"

Fixes #892.

Fix

Add aws_profile: str | None = None to _infer_region() and forward it to boto3.Session(profile_name=aws_profile). Update both AnthropicBedrock.__init__ and AsyncAnthropicBedrock.__init__ call sites from _infer_region() to _infer_region(aws_profile).

# before
session = boto3.Session()

# after
session = boto3.Session(profile_name=aws_profile)

The change is backward-compatible: when aws_profile is None (the default), boto3.Session(profile_name=None) behaves identically to boto3.Session().