refactor(python): use dedicated runtime environments

systems/brain/services/heater.nix

@@ -4,6 +4,20 @@
   ...
 }:
 {
+  nixpkgs.overlays = [
+    (final: _prev: {
+      heater_python = final.python314.withPackages (
+        ps: with ps; [
+          fastapi
+          pydantic
+          tinytuya
+          typer
+          uvicorn
+        ]
+      );
+    })
+  ];
+
   networking.firewall.allowedTCPPorts = [ 8124 ];
 
   systemd.services.heater-api = {
@@ -17,7 +31,7 @@
 
     serviceConfig = {
       Type = "simple";
-      ExecStart = "${pkgs.my_python}/bin/python -m python.heater.main --host 0.0.0.0 --port 8124";
+      ExecStart = "${pkgs.heater_python}/bin/python -m python.heater.main --host 0.0.0.0 --port 8124";
       EnvironmentFile = "/etc/heater.env";
       Restart = "on-failure";
       RestartSec = "5s";