heather/common: passwordless sudo for mikl + fix deprecated options

- common/default.nix: add mikl to wheel + security.sudo.wheelNeedsPassword=false.
  Without this, root is unreachable on a fresh NixOS-yc image (no root password,
  no rescue channel) — nixos-rebuild switch is impossible. Mirrors the
  NOPASSWD:ALL that old YC boxes got via cloud-config user-data.
- home/server.nix: programs.git.extraConfig -> .settings, programs.git.delta
  -> programs.delta with enableGitIntegration=true (deprecated warnings).
- image.nix: boot.loader.grub.timeout -> boot.loader.timeout (renamed option).

hosts/poppy/apps.nix

@@ -36,6 +36,7 @@
       "amneziavpn"
       "element"
       "prismlauncher"
+      "losslesscut"    # lossless-нарезка/remux видео (GUI на базе ffmpeg)
     ];
   };