feat: add Todoist tools to Shimmer and GPG signing for ultraviolet

- Update shimmer flake input (adds 7 Todoist tools, fixes devShell deps)
- Add TODOIST_API_TOKEN to shimmer-env secret
- Configure GPG signing key for ultraviolet host

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: joshsymonds

flake.lock

@@ -11,10 +11,7 @@
     inetutils
   ];
 
-  programs.git.settings.user = {
-    signingkey = "0x9920EB56D95D6CCF";
-    email = "josh+ultraviolet@joshsymonds.com";
-  };
+  programs.git.settings.user.signingkey = "0x374165B74CF6A70C";
 
   programs.zsh.shellAliases.update-bluedesert = "cd ~/nix-config && sudo env NIX_SSHOPTS='-i /home/joshsymonds/.ssh/github' nixos-rebuild switch --flake '.#bluedesert' --target-host joshsymonds@172.31.0.201 --sudo --option warn-dirty false";
 }