secrets: migrate all hosts from sops to OpenBao vault

Replace sops-nix secrets with OpenBao vault secrets across all hosts.
Hardcode root password hash, add extractKey option to vault-secrets
module, update Terraform with secrets/policies for all hosts, and
create AppRole provisioning playbook.

Hosts migrated: ha1, monitoring01, ns1, ns2, http-proxy, nix-cache01
Wave 1 hosts (nats1, jelly01, pgdb1) get AppRole policies only.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

hosts/http-proxy/configuration.nix

@@ -62,6 +62,8 @@
     "nix-command"
     "flakes"
   ];
+  vault.enable = true;
+
   nix.settings.tarball-ttl = 0;
   environment.systemPackages = with pkgs; [
     vim

hosts/http-proxy/wireguard.nix

@@ -1,9 +1,12 @@
 { config, ... }:
 {
-  sops.secrets.wireguard_private_key = {
-    sopsFile = ../../secrets/http-proxy/wireguard.yaml;
-    key = "wg_private_key";
+  vault.secrets.wireguard = {
+    secretPath = "hosts/http-proxy/wireguard";
+    extractKey = "private_key";
+    outputDir = "/run/secrets/wireguard_private_key";
+    services = [ "wireguard-wg0" ];
   };
+
   networking.wireguard = {
     enable = true;
     useNetworkd = true;
@@ -13,7 +16,7 @@
         ips = [ "10.69.222.3/24" ];
         mtu = 1384;
         listenPort = 51820;
-        privateKeyFile = config.sops.secrets.wireguard_private_key.path;
+        privateKeyFile = "/run/secrets/wireguard_private_key";
         peers = [
           {
             name = "docker2.t-juice.club";