Package Penpot 2.18.3 for Nix with NixOS module; afk devShell

Vendored from debling/nix-penpot (MIT). Fixes on top:
- pnpm fetchers: drop --config.fetch-* flags (UND_ERR_INVALID_ARG on pnpm 11.27)
  and pin real store hashes (frontend x3, exporter, mcp)
- deps-lock.json: add transitive funcool/beicon2 v2.0 so fake-git resolves
  potok2's pin during the shadow-cljs classpath build
- expose frontend pnpm stores via passthru for rehashing
- x86_64-linux only; devShell ships afk, jj, git

.gitignore

@@ -0,0 +1,5 @@
+.direnv/
+/result
+/result-*
+/penpot
+/penpot-vm.qcow2