[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/shadowsocks/module/main.tf

@@ -0,0 +1,106 @@
+variable "password" {}
+variable "tier" { type = string }
+variable "method" {
+  default = "chacha20-ietf-poly1305"
+}
+
+resource "kubernetes_namespace" "shadowsocks" {
+  metadata {
+    name = "shadowsocks"
+    labels = {
+      tier = var.tier
+    }
+    # TLS termination seems iffy - I get pfsense MiTM-ing
+    # labels = {
+    #   "istio-injection" : "enabled"
+    # }
+  }
+}
+
+resource "kubernetes_deployment" "shadowsocks" {
+  metadata {
+    name      = "shadowsocks"
+    namespace = kubernetes_namespace.shadowsocks.metadata[0].name
+    labels = {
+      "app" = "shadowsocks"
+      tier  = var.tier
+    }
+    annotations = {
+      "reloader.stakater.com/search" = "true"
+    }
+  }
+  spec {
+    replicas = "1"
+    selector {
+      match_labels = {
+        "app" = "shadowsocks"
+      }
+    }
+    template {
+      metadata {
+        labels = {
+          "app" = "shadowsocks"
+        }
+      }
+      spec {
+        container {
+          name              = "shadowsocks"
+          image             = "shadowsocks/shadowsocks-libev"
+          image_pull_policy = "IfNotPresent"
+          env {
+            name  = "METHOD"
+            value = var.method
+          }
+          env {
+            name  = "PASSWORD"
+            value = var.password
+          }
+          port {
+            container_port = 8388
+            protocol       = "TCP"
+          }
+          port {
+            container_port = 8388
+            protocol       = "UDP"
+          }
+        }
+      }
+    }
+  }
+}
+
+resource "kubernetes_service" "mailserver" { # rename me
+  metadata {
+    name      = "shadowsocks"
+    namespace = kubernetes_namespace.shadowsocks.metadata[0].name
+
+    labels = {
+      app = "shadowsocks"
+    }
+    annotations = {
+      "metallb.universe.tf/allow-shared-ip" = "shared"
+    }
+  }
+
+  spec {
+    type                    = "LoadBalancer"
+    external_traffic_policy = "Cluster"
+    selector = {
+      app = "shadowsocks"
+    }
+
+    port {
+      name        = "shadowsocks-tcp"
+      protocol    = "TCP"
+      port        = 8388
+      target_port = "8388"
+    }
+
+    port {
+      name        = "shadowsocks-udp"
+      protocol    = "UDP"
+      port        = 8388
+      target_port = "8388"
+    }
+  }
+}