feat: add smart alerting and noatime to disks

hosts/nas/modules/power-management.nix

@@ -0,0 +1,19 @@
+# Power management for NAS
+# - CPU powersave governor (scales up on demand for transcoding)
+# - Disk spindown after 15 minutes idle
+{ config, lib, pkgs, ... }:
+
+{
+  # CPU Power Management - powersave scales up on demand for transcoding
+  powerManagement.cpuFreqGovernor = "powersave";
+
+  # Disk spindown - hdparm for Seagate 18TB drives
+  environment.systemPackages = [ pkgs.hdparm ];
+
+  services.udev.extraRules = ''
+    # Seagate 18TB NAS drives - APM 127 allows spindown, -S 180 = 15 min
+    ACTION=="add", KERNEL=="sd[a-z]", SUBSYSTEM=="block", \
+      ATTRS{model}=="ST18000NM000J*", \
+      RUN+="${pkgs.hdparm}/bin/hdparm -B 127 -S 180 /dev/%k"
+  '';
+}