Initial import of HortusFox Nix flake packaging

Packages HortusFox from source via php.buildComposerProject and provides
a NixOS module (services.hortusfox-web) to deploy it as a full service
(mariadb + phpfpm + nginx/caddy + ACME + cron timers).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.nix

@@ -0,0 +1,30 @@
+{ lib, php, fetchFromGitHub, ... }:
+
+# buildComposerProject installs the project to
+#   $out/share/php/<pname>/  (with vendor/ populated)
+php.buildComposerProject (finalAttrs: {
+  pname = "hortusfox-web";
+  version = "5.9";
+
+  src = fetchFromGitHub {
+    owner = "danielbrendel";
+    repo = "hortusfox-web";
+    rev = "v${finalAttrs.version}";
+    hash = "sha256-O4I25YntVL+UwWATRiI5h9MYkVeN7JEmrRLt0eVwMTs=";
+  };
+
+  # composer.lock is committed upstream, so a fixed vendorHash works.
+  vendorHash = "sha256-b9t5S12TJoiup7fkQ4bo2xH+CvEt6MqOrQxQ/gJ4Deg=";
+
+  # No console entrypoint to expose on PATH; we call `php asatru` ourselves.
+  composerNoDev = true;
+
+  composerStrictValidation = false;
+
+  meta = with lib; {
+    description = "Self-hosted collaborative plant management system";
+    homepage = "https://github.com/danielbrendel/hortusfox-web";
+    license = licenses.mit;
+    platforms = platforms.linux;
+  };
+})