feat(infra): distribute terraform modules under infra/terraform

POC: lift the homelab-grown nextcloud-mcp-server and
nextcloud-mcp-deployer-role Terraform modules into this repo so external
operators can consume them via a `git::` source.

Includes a top-level README documenting the two-phase deploy flow
(bootstrap deployer role with a copy-pasteable IAM policy, then assume the
role to deploy the MCP server) and supports both in-VPC Qdrant and
external/managed Qdrant modes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

infra/terraform/nextcloud-mcp-server/service_discovery.tf

@@ -0,0 +1,5 @@
+resource "aws_service_discovery_private_dns_namespace" "this" {
+  name        = "${var.name}.local"
+  description = "Private DNS namespace for ${var.name} internal services"
+  vpc         = var.vpc_id
+}