sops-nix bootstrap + Forgejo at git.tyrolize.ch

sops:
- devShell provides ssh-to-age and sets SOPS_AGE_KEY_FILE to
  $REPO/.sops-age-key.txt (gitignored, generated locally).
- .sops.yaml lists laptop + watcher recipients. The watcher recipient is
  derived from /etc/ssh/ssh_host_ed25519_key.pub via ssh-to-age, so the
  watcher decrypts using its SSH host key as the age identity at boot.
- hosts/watcher/secrets.yaml holds an `example` placeholder; sops-install-
  secrets surfaces it at /run/secrets/example (root-only).

Forgejo:
- modules/forgejo.nix enables services.forgejo (sqlite + daily tar.gz
  dump), built-in SSH server on :2222, HTTP on 127.0.0.1:3000.
- modules/website.nix adds the git.tyrolize.ch vhost reverse-proxying to
  localhost. Caddy gets a Let's Encrypt cert automatically.
- terraform/infomaniak/watcher.tf opens :2222 v4+v6 in the security group.
- Admin user `tyro` (role admin) created out-of-band via the gitea CLI.

Both services live on the watcher.

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

flake.nix

@@ -23,13 +23,15 @@
           opentofu          # `tofu` — drop-in for terraform, OSS license
           jq
           age
-          sops              # for sops-nix secrets
+          sops              # encrypted secrets, paired with sops-nix
+          ssh-to-age        # convert an SSH host key to an age recipient
         ];
         shellHook = ''
           if [ -f "$PWD/terraform/infomaniak/.env" ]; then
             set -a; . "$PWD/terraform/infomaniak/.env"; set +a
             echo "loaded terraform/infomaniak/.env"
           fi
+          export SOPS_AGE_KEY_FILE="$PWD/.sops-age-key.txt"
         '';
       };