[ci skip] Move Terraform modules into stack directories

Move all 88 service modules (66 individual + 22 platform) from
modules/kubernetes/<service>/ into their corresponding stack directories:

- Service stacks: stacks/<service>/module/
- Platform stack: stacks/platform/modules/<service>/

This collocates module source code with its Terragrunt definition.
Only shared utility modules remain in modules/kubernetes/:
ingress_factory, setup_tls_secret, dockerhub_secret, oauth-proxy.

All cross-references to shared modules updated to use correct
relative paths. Verified with terragrunt run --all -- plan:
0 adds, 0 destroys across all 68 stacks.

stacks/platform/modules/metallb/main.tf

@@ -0,0 +1,40 @@
+# Creates namespace and everythin needed
+# Do not use until https://github.com/colinwilson/terraform-kubernetes-metallb/issues/5 is solved
+# module "metallb" {
+#   source  = "colinwilson/metallb/kubernetes"
+#   version = "0.1.7"
+# }
+variable "tier" { type = string }
+
+resource "kubernetes_namespace" "metallb" {
+  metadata {
+    name = "metallb-system"
+    labels = {
+      app = "metallb"
+      # "istio-injection" : "disabled"
+      # tier = var.tier
+    }
+  }
+}
+
+module "metallb" {
+  source     = "ViktorBarzin/metallb/kubernetes"
+  version    = "0.1.5"
+  depends_on = [kubernetes_namespace.metallb]
+}
+
+resource "kubernetes_config_map" "config" {
+  metadata {
+    name      = "config"
+    namespace = kubernetes_namespace.metallb.metadata[0].name
+  }
+  data = {
+    config = <<EOT
+address-pools:
+- name: default
+  protocol: layer2
+  addresses:
+  - 10.0.20.200-10.0.20.220
+EOT
+  }
+}