feat(edge): Terraform for the China-facing relay and Cloudflare DNS

Adds terraform/edge, a root module with two providers:

- Cloudflare 5.28.1: CNAMEs to the existing tunnel, plus an opt-in resource that
  can take the tunnel ingress list over when manage_tunnel_config is true. It is
  off by default because that resource REPLACES the whole list, and the tunnel is
  remotely managed from the dashboard today.
- Tencent Cloud 1.83.38: VPC, subnet, security group with three rules, key pair,
  one CVM relay with cloud-init (WireGuard listener, forwarding sysctls, Caddy),
  and DNSPod A records for the .cn hostnames.

The design keeps the homelab inbound-free: the relay terminates TLS in China and
forwards over a WireGuard tunnel the cluster dials outbound. Cloudflare keeps
serving every existing hostname untouched.

Verified: terraform init succeeds for both providers, fmt clean, validate
reports 0 errors, and plan resolves to 10 creates with placeholder variables.
Provider-side name validation caught a real bug during that run: key pair and
security group names allow only letters, digits and underscore, so the derived
names use underscores.

Not applied. Credentials come from CLOUDFLARE_API_TOKEN,
TENCENTCLOUD_SECRET_ID and TENCENTCLOUD_SECRET_KEY; the WireGuard private key is
TF_VAR only. State is local and git-ignored like terraform/zitadel.

Blocked on facts this module cannot invent: the real .cn domain, whether it has
an ICP filing, the CVM image ID, the operator CIDR, and the homelab WireGuard
public key.

terraform/edge/providers.tf

@@ -0,0 +1,47 @@
+# terraform/edge — the China-facing edge, plus DNS ownership for the existing zone
+#
+# Purpose: give users in mainland China a short, stable path to the homelab
+# without touching the Cloudflare path that serves everyone else.
+#
+#   China user -> <service>.<china_domain> -> Tencent CVM (this module)
+#              -> WireGuard tunnel -> ingress-nginx (192.168.1.160) -> service
+#
+#   Everyone else -> Cloudflare -> cloudflared tunnel -> same ingress (unchanged)
+#
+# The homelab still opens no inbound port: the tunnel is established outbound
+# from the cluster to the CVM.
+#
+# Credentials come from the environment, never from a file in git:
+#   export CLOUDFLARE_API_TOKEN=...
+#   export TENCENTCLOUD_SECRET_ID=...
+#   export TENCENTCLOUD_SECRET_KEY=...
+#   terraform -chdir=terraform/edge init
+#   terraform -chdir=terraform/edge plan -var china_domain=example.cn ...
+#
+# State is local and git-ignored, same as terraform/zitadel. It carries no
+# credential today, but it will once InstanceData or certificates are added, so
+# treat it as a secret and move it to MinIO before a second operator applies.
+terraform {
+  required_version = ">= 1.6.0"
+
+  required_providers {
+    cloudflare = {
+      source  = "cloudflare/cloudflare"
+      version = "5.28.1"
+    }
+    tencentcloud = {
+      source  = "tencentcloudstack/tencentcloud"
+      version = "1.83.38"
+    }
+  }
+}
+
+provider "cloudflare" {
+  api_token = var.cloudflare_api_token
+}
+
+provider "tencentcloud" {
+  secret_id  = var.tencent_secret_id
+  secret_key = var.tencent_secret_key
+  region     = var.tencent_region
+}