add aspects/hosts/ configurations

Host-specific NixOS configurations for:
- alexandria (server)
- io (desktop)
- rotterdam (desktop)
- trantor (server, aarch64)

Each host has a main config file and _hostname/ directory
with hardware-configuration and other host-specific modules.

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

aspects/hosts/_trantor/forgejo.nix

@@ -0,0 +1,72 @@
+{
+  config,
+  lib,
+  inputs,
+  ...
+}:
+
+let
+  utils = import ../../../utils.nix { inherit inputs lib; };
+  inherit (utils) mkNginxVHosts;
+in
+
+{
+  services = {
+    forgejo = {
+      enable = true;
+      settings = {
+        session.COOKIE_SECURE = true;
+        server = {
+          PROTOCOL = "http+unix";
+          DOMAIN = "git.baduhai.dev";
+          ROOT_URL = "https://git.baduhai.dev";
+          OFFLINE_MODE = true; # disable use of CDNs
+          SSH_DOMAIN = "git.baduhai.dev";
+        };
+        log.LEVEL = "Warn";
+        mailer.ENABLED = false;
+        actions.ENABLED = false;
+        service.DISABLE_REGISTRATION = true;
+        oauth2_client = {
+          ENABLE_AUTO_REGISTRATION = true;
+          UPDATE_AVATAR = true;
+          ACCOUNT_LINKING = "login";
+          USERNAME = "preferred_username";
+        };
+      };
+    };
+    nginx.virtualHosts = mkNginxVHosts {
+      domains."git.baduhai.dev".locations."/".proxyPass =
+        "http://unix:${config.services.forgejo.settings.server.HTTP_ADDR}:/";
+    };
+    fail2ban.jails.forgejo = {
+      settings = {
+        enabled = true;
+        filter = "forgejo";
+        maxretry = 3;
+        findtime = "10m";
+        bantime = "1h";
+      };
+    };
+  };
+
+  environment = {
+    etc."fail2ban/filter.d/forgejo.conf".text = ''
+      [Definition]
+      failregex = .*(Failed authentication attempt|invalid credentials|Attempted access of unknown user).* from <HOST>
+      ignoreregex =
+      journalmatch = _SYSTEMD_UNIT=forgejo.service
+    '';
+
+    persistence.main.directories = [
+      {
+        directory = config.services.forgejo.stateDir;
+        inherit (config.services.forgejo) user group;
+        mode = "0700";
+      }
+    ];
+  };
+
+  # Disable PrivateMounts to allow LoadCredential to work with bind-mounted directories
+  systemd.services.forgejo.serviceConfig.PrivateMounts = lib.mkForce false;
+}