refactor(terraform): decouple NFS, PostgreSQL, ActiveMQ setup into own Terraform roots — Layer 3

[bhumi46]

Part of #273

What

Extract nfs-setup, postgresql-setup, and activemq-setup modules each into their own standalone Terraform root.

Why

Currently these are chained sequentially via depends_on — even if only PostgreSQL config needs updating, the entire chain from aws-resource-creation is evaluated. Each should be independently re-runnable.

Acceptance Criteria

• nfs, postgresql, activemq are standalone Terraform roots under terraform/implementations/aws/
• Each reads required IPs via data "aws_instance" by tag
• Each can be triggered and re-run independently
• postgresql and activemq retain their existing enable_* conditional behaviour