Harden server and add Nix-native CI + self-hosted Gitea Actions

- caddy: security headers (X-Content-Type-Options/X-XSS-Protection/
  X-Frame-Options) on all vhosts + baseline CSP; strip SnappyMail
  upstream copies via header_down on mail.severijnse.eu
- tlsa-updater: compute TLSA 3 1 1 from cert SPKI (SHA-256), sync
  _25/_465/_993, fail-safe placeholders; coredns zone updated
- pre-commit: wire cachix/git-hooks.nix (alejandra, statix, actionlint,
  ...); CI pre-commit job over x86_64 + aarch64 matrix
- gitea: enable Gitea Actions + self-hosted runner (native:host,
  aarch64 via binfmt); add .gitea/workflows/ci.yml and local hook
- fix statix warnings (merge repeated systemd/database/configFile keys,
  inherit, bool-compare guards); add missing trailing newlines

servers/hetzner/modules/services/gitea.nix

@@ -5,50 +5,85 @@
   unstablePkgs,
   ...
 }: {
-  services.postgresql = {
-    enable = true;
-    package = pkgs.postgresql_14;
-    ensureDatabases = ["gitea"];
-    ensureUsers = [
-      {
+  services = {
+    postgresql = {
+      enable = true;
+      package = pkgs.postgresql_14;
+      ensureDatabases = ["gitea"];
+      ensureUsers = [
+        {
+          name = "gitea";
+          ensureDBOwnership = true;
+        }
+      ];
+    };
+
+    gitea = {
+      enable = true;
+      package = unstablePkgs.gitea;
+      database = {
+        type = "postgres";
         name = "gitea";
-        ensureDBOwnership = true;
-      }
-    ];
+        user = "gitea";
+      };
+      appName = "Jory's Git";
+      lfs.enable = true;
+      settings = {
+        server = {
+          DOMAIN = "git.severijnse.eu";
+          ROOT_URL = "https://git.severijnse.eu/";
+          HTTP_PORT = 3000;
+          SSH_PORT = 222;
+          SSH_LISTEN_PORT = 2222;
+          START_SSH_SERVER = true;
+          SSH_USER = "git";
+          BUILTIN_SSH_SERVER_USER = "git";
+          LANDING_PAGE = "explore";
+        };
+        service = {
+          DISABLE_REGISTRATION = true;
+          REQUIRE_SIGNIN_VIEW = false;
+        };
+        repository = {
+          DEFAULT_BRANCH = "main";
+        };
+        actions = {
+          ENABLED = true;
+        };
+      };
+    };
+
+    gitea-actions-runner = {
+      # nixos-24-05's gitea-actions-runner module hardcodes bin/act_runner,
+      # but the current upstream package (1.0.3, matching gitea 1.26) ships
+      # bin/gitea-runner. Wrap it so both names resolve.
+      package = pkgs.runCommand "gitea-actions-runner-wrapped" {} ''
+        mkdir -p $out/bin
+        ln -s ${unstablePkgs.gitea-actions-runner}/bin/gitea-runner $out/bin/act_runner
+      '';
+      instances.default = {
+        enable = true;
+        name = "hetzner";
+        url = "https://git.severijnse.eu";
+        tokenFile = "/var/lib/secrets/gitea-runner-token";
+        labels = ["native:host"];
+        hostPackages = with pkgs; [
+          bash
+          coreutils
+          curl
+          gawk
+          gitMinimal
+          gnused
+          nodejs
+          wget
+        ];
+      };
+    };
   };
 
   # Gitea connects to local Postgres via Unix socket (peer auth).
   # No password needed — the socket is at /run/postgresql by default.
   # createDatabase = true ensures the DB + user are set up automatically.
-  services.gitea = {
-    enable = true;
-    package = unstablePkgs.gitea;
-    database.type = "postgres";
-    database.name = "gitea";
-    database.user = "gitea";
-    appName = "Jory's Git";
-    lfs.enable = true;
-    settings = {
-      server = {
-        DOMAIN = "git.severijnse.eu";
-        ROOT_URL = "https://git.severijnse.eu/";
-        HTTP_PORT = 3000;
-        SSH_PORT = 222;
-        SSH_LISTEN_PORT = 2222;
-        START_SSH_SERVER = true;
-        SSH_USER = "git";
-        BUILTIN_SSH_SERVER_USER = "git";
-        LANDING_PAGE = "explore";
-      };
-      service = {
-        DISABLE_REGISTRATION = true;
-        REQUIRE_SIGNIN_VIEW = false;
-      };
-      repository = {
-        DEFAULT_BRANCH = "main";
-      };
-    };
-  };
 
   # Gitea built-in SSH server: listens on high port 2222 (no privileged-cap needed),
   # while clone URLs advertise port 222. Firewall redirects 222 -> 2222.
@@ -61,4 +96,10 @@
     ${pkgs.nftables}/bin/nft add chain inet gitea-redirect prerouting '{ type nat hook prerouting priority dstnat; }' 2>/dev/null || true
     ${pkgs.nftables}/bin/nft add rule inet gitea-redirect prerouting tcp dport 222 redirect to :2222 2>/dev/null || true
   '';
+
+  # --- Gitea Actions self-hosted CI runner ---
+  # Jobs install their own Nix inside the runner (official installer,
+  # --no-daemon) so no system Nix daemon / nix-users group is needed.
+  # aarch64 builds run under QEMU user-emulation via boot.binfmt below.
+  boot.binfmt.emulatedSystems = ["aarch64-linux"];
 }