feat(cfn): Add CloudWatch Logs retention parameter

[Copilot]

Lambda functions create log groups with indefinite retention by default. This adds a CloudFormation parameter to control log retention period with a default of 14 days.

Changes

• New parameter: LogRetentionInDays with default value of 14, accepting all CloudFormation-supported retention periods (1-3653 days)
• New resource: LambdaLogGroup explicitly creates the log group with configurable retention before Lambda initialization
• Updated: .aws/README.md with parameter documentation and deployment examples

Usage

Parameters:
  LogRetentionInDays:
    Type: Number
    Default: 14
    Description: 'CloudWatch Logs retention period in days'

Deploy with custom retention:

aws cloudformation create-stack \
  --stack-name hono-lambda-poc-service \
  --template-body file://cfn-service.yml \
  --parameters \
    ParameterKey=ImageUri,ParameterValue=<ECR_IMAGE_URI> \
    ParameterKey=LogRetentionInDays,ParameterValue=30 \
  --capabilities CAPABILITY_NAMED_IAM

The explicit log group resource ensures CloudFormation manages the full lifecycle, including retention settings and cleanup on stack deletion.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>cfn-serviceでCloudWatch Logsのretentionを指定するようにしたい</issue_title>
<issue_description>- CFnのパラメータにできると良い

• デフォルトは14日 (2週間) としたい。</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes cfn-serviceでCloudWatch Logsのretentionを指定するようにしたい #16

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