refactor(python): use dedicated runtime environments

systems/jeeves/services/gems.nix

@@ -8,6 +8,22 @@ let
   stateDir = "${vars.services}/gems";
 in
 {
+  nixpkgs.overlays = [
+    (final: _prev: {
+      gems_python = final.python314.withPackages (
+        ps: with ps; [
+          fastapi
+          jinja2
+          pydantic
+          pydantic-settings
+          python-multipart
+          typer
+          uvicorn
+        ]
+      );
+    })
+  ];
+
   users.groups.gems = { };
   users.users.gems = {
     isSystemUser = true;
@@ -36,7 +52,7 @@ in
       Type = "simple";
       User = "gems";
       Group = "gems";
-      ExecStart = "${pkgs.my_python}/bin/python -m python.gems.main --host 0.0.0.0 --port 8002";
+      ExecStart = "${pkgs.gems_python}/bin/python -m python.gems.main --host 0.0.0.0 --port 8002";
       Restart = "on-failure";
       RestartSec = "5s";
       StandardOutput = "journal";