fix: resolve Lambda invocation failure from API Gateway

- Align Dockerfile with AWS official documentation for provided runtime
- Remove DefinitionBody from SAM template to avoid conflict with Events property
- This enables SAM to automatically generate AWS::Lambda::Permission resource
- Fixes 500 error when Forgejo webhook triggers API Gateway endpoint"

infra/cfn/template-lambda-function.yaml

@@ -105,29 +105,6 @@ Resources:
       Name: blog-deployment-webhook-api
       StageName: !Ref StageName
       EndpointConfiguration: REGIONAL
-      DefinitionBody:
-        openapi: "3.0.1"
-        info:
-          title: "Forgejo Webhook API"
-          version: "1.0"
-        paths:
-          /forgejo-webhook:
-            post:
-              summary: "Trigger Lambda via Forgejo Webhook"
-              x-amazon-apigateway-integration:
-                uri:
-                  Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${MyLambdaFunction.Arn}/invocations
-                httpMethod: POST
-                type: aws_proxy
-              responses:
-                '200':
-                  description: "Successful response"
-                '400':
-                  description: "Bad Request - Incorrect request payload format"
-                '401':
-                  description: "Unauthorized - Signature verification failed"
-                '500':
-                  description: "Server error - Deployment process failed"
 
 Outputs:
   ApiEndpoint: