Add flowtrack period tracker

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

services/flowtrack.nix

@@ -0,0 +1,21 @@
+# services/flowtrack.nix — Kayla's private period tracker.
+#
+# The application and NixOS module live in the standalone flowtrack flake.
+# nginx is the only public listener and Authelia admits just kayla and fred;
+# the app maps them to owner and read-only viewer. Nightly snapshots go
+# straight to the SSD branch of the pool (not via mergerfs), which had the
+# cleanest SMART record of the data disks.
+{ config, lib, ... }:
+{
+  config = lib.mkIf (config.networking.hostName == "FredOS-Mediaserver") {
+    services.flowtrack = {
+      enable = true;
+      port = 8093;
+      editors = [ "kayla" ];
+      viewers = [ "fred" ];
+      backup.directory = "/mnt/disk2/backups/flowtrack";
+    };
+
+    systemd.tmpfiles.rules = [ "d /mnt/disk2/backups 0755 root root -" ];
+  };
+}