Set ECS host metadata hop limit to 1

[ale210]

Fixes #251.

Adds metadata_options to aws_launch_template.ecs with http_put_response_hop_limit = 1, so containers on Docker's bridge network cannot fetch ecs-ec2-role's credentials from instance metadata. Must land before any service moves to bridge mode (#252–#254).

Expected plan: aws_launch_template.ecs updated in place (mints version 9), 0 to add, 0 to destroy. default_version stays 1; the ASG launches from $Latest. The user_data and default_version comments are updated because both named version 8.

This does not touch the two running instances. After merge they get the same setting by hand with modify-instance-metadata-options, one at a time — see the issue.

Validated locally with Terraform 1.16.0: init -backend=false, validate, and fmt -check on compute.tf.

[github-actions]

Terraform plan in terraform
With backend config files: terraform/prod.backend.tfvars

Plan: 0 to add, 1 to change, 0 to destroy.

Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
!~  update in-place

Terraform will perform the following actions:

  # module.platform.aws_launch_template.ecs will be updated in-place
!~  resource "aws_launch_template" "ecs" {
        id                                   = "lt-0093b22d4b048e101"
!~      latest_version                       = 8 -> (known after apply)
        name                                 = "ecs-incubator-prod"
        tags                                 = {}
#        (18 unchanged attributes hidden)

+       metadata_options {
+           http_endpoint               = "enabled"
+           http_put_response_hop_limit = 1
+           http_tokens                 = "********"
        }

#        (1 unchanged block hidden)
    }

Plan: 0 to add, 1 to change, 0 to destroy.

✅ Plan applied in Terraform apply (OIDC) #99