nix: one Hetzner host for the CI server + the orchestrator (#cc-ci)

The orchestrator's flake now builds the machine it shares with the cc-ci CI
server: `nixosConfigurations.cc-ci` composes cc-ci's nixosModules.cc-ci-server
(new flake input, nixpkgs + sops-nix follow ours), this repo's orchestrator
module (nix/modules/cc-ci.nix, exported as cc-ci-orchestrator, `cc-ci` kept
as an alias for notplants-nix) and the new nix/modules/orchestrator-host.nix
— the host contract those units always assumed (loops user, claude/opencode
CLIs, opencode web server + tailnet-only UI on 8443 since traefik owns
80/443, nix-ld, tool set, `ssh cc-ci` → loopback).

nix/hosts/cc-ci/{hardware,networking}.nix are PROVISIONAL copies of the old
server's layout so the flake evaluates; they get replaced by the
nixos-infect output of 195.201.88.249.

README.md is the deploy guide (Hetzner Debian → nixos-infect → this flake →
staging → data restore → cutover). archive/ holds the retired Incus/Hetzner
orchestrator host configs, the old terraform and the migration plans;
references updated. cc-ci-plan/plan-cc-ci-combined-host.md is the working
plan for the move.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FqkQq3CDmFWcQ7u1LzoyRz

archive/terraform/versions.tf

@@ -0,0 +1,14 @@
+terraform {
+  required_version = ">= 1.0"
+  required_providers {
+    hcloud = {
+      source  = "hetznercloud/hcloud"
+      version = "1.64.0"
+    }
+  }
+}
+
+# The hcloud provider reads HCLOUD_TOKEN from the environment automatically.
+# Never put the token value in any .tf file or .tfvars — keep it in the shell
+# environment (export HCLOUD_TOKEN=...) or pass via TF_VAR_hcloud_token.
+provider "hcloud" {}