feat(infrastructure): add scaffolding for the infrastructure kind

[Nageshbansal]

Adds scaffolding for the third casting kind, Infrastructure: schema, types, pipeline wiring, and a first casting. The installation migration follows separately.

Features

• Adds KindInfrastructure with its own api package and per-kind schema. Spec is deployment, resource and patches.
• spec.resource declares which kind the infrastructure serves (Installation or CollectionAgent). Nothing else: the installation owns the binding and declares it on its own casting, so no name or apiVersion here, and nothing is read from the other casting.
• Adds resourcemolding: writes what the declared kind needs into resource.status (ports as addresses; storage and node sizing in the resource.yaml config).
• Adds awskubernetesterraformcasting: forges an EKS setup under pours/infrastructure/ (VPC, cluster, one node group, EBS CSI addon when the kind needs storage). Node sizes are written as vcpus and memory and resolved to an instance type by terraform at plan time; a variable pins an exact type.
• Wires the kind through the loader, lock, planner registry and schema generation.
• Re-types installation's spec.infrastructure to the binding: {name} of the infrastructure casting it runs on. The consumer owns the reference; the infrastructure declares only the kind it serves. Breaking for any casting that set the old enabled/status fields; the ledger shows zero ever did.
• Removes the inline terraform generation path it replaces (internal/infrastructure, the forge special case, the per-component aws/gcp/azure templates).
• Adds docs/examples/aws/kubernetes/terraform/.

Out of scope

• Cast(): logs the terraform steps instead of running them.

Example

# casting.yaml
apiVersion: v1alpha1
kind: Infrastructure
metadata:
  name: signoz
spec:
  deployment:
    platform: aws
    mode: kubernetes
    flavor: terraform
  resource:
    kind: Installation

# casting.yaml.lock
apiVersion: v1alpha1
kind: Infrastructure
metadata:
  name: signoz
spec:
  deployment:
    flavor: terraform
    mode: kubernetes
    platform: aws
  resource:
    kind: Installation
    status:
      addresses:
        apiserver:
        - tcp://0.0.0.0:8080
        otlp:
        - tcp://0.0.0.0:4317
        - tcp://0.0.0.0:4318
      config:
        data:
          resource.yaml: |
            nodeGroups:
            - count: 2
              disk: 50
              memory: 8
              name: default
              vcpus: 2
            storage:
              persistent: true

Tests

• Schema validation for the resource declaration.
• Molding dispatch per resource kind and merge of enricher contributions.
• Loader dispatch for the new kind, including absent resource and self-reference.
• Template rendering per resource kind; the generated terraform passes terraform validate.