feat: simplify blog lambda deployment pipeline

infra/cfn/template-lambda-function.yaml

@@ -22,14 +22,6 @@ Parameters:
     Default: main
     Description: Git repository branch
 
-  ImageDigest:
-    Type: String
-    Default: ""
-    Description: "ECR image digest (e.g., sha256:abc123...). If empty, uses 'latest' tag. Use digest for deterministic deployments."
-
-Conditions:
-  UseDigest: !Not [!Equals [!Ref ImageDigest, ""]]
-
 Resources:
 
   MyLambdaRole:
@@ -79,15 +71,9 @@ Resources:
     Properties:
       FunctionName: blog-deployment-webhook-handler
       PackageType: Image
-      ImageUri: !If
-        - UseDigest
-        - !Sub
-          - "${RepoUri}@${Digest}"
-          - RepoUri: !ImportValue BlogDeployment-RepositoryUri
-            Digest: !Ref ImageDigest
-        - !Sub
-          - "${RepoUri}:latest"
-          - RepoUri: !ImportValue BlogDeployment-RepositoryUri
+      ImageUri: !Sub
+        - "${RepoUri}:latest"
+        - RepoUri: !ImportValue BlogDeployment-RepositoryUri
       Timeout: 300
       MemorySize: 512
       Architectures: