refactor(python): use dedicated runtime environments

systems/jeeves/runners/nix_builder.nix

@@ -23,6 +23,13 @@ let
       ...
     }:
     let
+      giteaAutomationPython = pkgs.python314.withPackages (
+        ps: with ps; [
+          httpx
+          pydantic
+          typer
+        ]
+      );
       runnerConfigFile = (pkgs.formats.yaml { }).generate "gitea-runner.yaml" { };
       registerRunner = pkgs.writeShellApplication {
         name = "register-gitea-runner";
@@ -96,8 +103,8 @@ let
           curl
           gawk
           gitMinimal
+          giteaAutomationPython
           gnused
-          my_python
           nix
           nixfmt
           nixos-rebuild