Add omasnap upstream repository to flake inputs

[Copilot]

Issue asks to add https://github.com/tobi/omasnap into the Nix configuration so it is available from this repo’s flake setup. This PR introduces that source as a minimal, focused config update.

• Flake input addition

  • Added a new inputs.omasnap entry in flake.nix.
  • Marked it as a non-flake source to match the upstream repository structure.

• Scope

  • No host/user/module wiring changes in this PR.
  • Change is limited to making the upstream source available in the flake input graph for downstream consumption.

omasnap = {
  url = "github:tobi/omasnap";
  flake = false;
};

• Fixes https://github.com/tobi/omasnap #128

[dezren39]

@copilot are you messing with me