Hardening: Vulnix + kernel hardening

Signed-off-by: Hadi <hadi@example.fr>

hosts/laptop/configuration.nix

@@ -14,6 +14,7 @@
     ../../nixos/utils.nix
     ../../nixos/hyprland.nix
     ../../nixos/steam.nix
+    ../../nixos/kernel-hardening.nix
     ../../home/programs/gui/helium/system.nix # I hate browser's configuration..
 
     # CHANGEME: You should probably remove those things:

hosts/laptop/persistence.nix

@@ -13,6 +13,7 @@
       "/var/lib/systemd/timers" # last-run timestamps (e.g. nix gc weekly)
       "/var/log"
       "/var/cache/tuigreet"
+      "/var/cache/vulnix"
       "/var/db/sudo/lectured" # remembers that the sudo lecture was already shown
     ];