docs: update deployment instructions and enhance ECR push script

deployment/BedrockProxy.template

@@ -4,6 +4,9 @@ Parameters:
     Type: String
     AllowedPattern: ^arn:aws:secretsmanager:.*$
     Description: The secret ARN in Secrets Manager used to store the API Key
+  ContainerImageUri:
+    Type: String
+    Description: The ECR image URI for the Lambda function (e.g., 123456789012.dkr.ecr.us-east-1.amazonaws.com/bedrock-proxy-api:latest)
   DefaultModelId:
     Type: String
     Default: anthropic.claude-3-sonnet-20240229-v1:0
@@ -169,13 +172,7 @@ Resources:
         - arm64
       Code:
         ImageUri:
-          Fn::Join:
-            - ""
-            - - 366590864501.dkr.ecr.
-              - Ref: AWS::Region
-              - "."
-              - Ref: AWS::URLSuffix
-              - /bedrock-proxy-api:latest
+          Ref: ContainerImageUri
       Description: Bedrock Proxy API Handler
       Environment:
         Variables: