feat: add btrfs + btrbk module for 16TB data disk

- New module: modules/nixos/filesystem/temp-16tb-disk.nix with btrfs kernel support, btrfs-progs + btrbk, LUKS2 auto-unlock, nofail mount, btrbk daily snapshots (14d/4w/3m)
- Registered in flake.nix for lazyworkhorse
- Host config with commented-out enable block (fill UUID when disk reconnected)

hosts/lazyworkhorse/configuration.nix

@@ -8,6 +8,14 @@
   # NAS Mounting
   hoardingcow-mount.enable = true;
 
+  # 16TB btrfs storage disk (WD Red Pro — LUKS2 + btrfs + btrbk snapshots)
+  # ⚠ SETUP REQUIRED: Connect the disk, get the LUKS UUID with 'blkid /dev/sdb',
+  #   then set gortium.temp16tb.luksUuid here and deploy.
+  # gortium.temp16tb = {
+  #   enable = true;
+  #   luksUuid = "REPLACE_ME_WITH_REAL_UUID";
+  # };
+
   # Flakesss
   nix.settings.experimental-features = [ "nix-command" "flakes" "flake-self-attrs" ];
   nix.settings.trusted-users = [ "root" "gortium" ];