Restructure project layout and add ECR repository CloudFormation template

- Move application entrypoint to cmd/lambda/
- Move Dockerfile to docker/ for clearer build context separation
- Promote go.mod/go.sum to project root
- Move CloudFormation templates under infra/cfn/ for consistent infra layout
- Add new template-container-repository.yaml defining ECR repository (blog-deployment)
- Move Lambda test files to test/ directory

template-blog-source-bucket.yaml

@@ -1,19 +0,0 @@
-AWSTemplateFormatVersion: '2010-09-09'
-
-Parameters:
-  BucketName:
-    Type: String
-    Description: "The name for the S3 bucket to be used for public website hosting (must be globally unique)"
-    Default: "naputo-blog-source"
-
-Resources:
-
-  SourceBucket:
-    Type: AWS::S3::Bucket
-    Properties:
-      BucketName: !Ref BucketName
-      Tags:
-        - Key: Project
-          Value: Git-server
-      VersioningConfiguration:
-        Status: Enabled