Add symfony package, expand php definition, add native zsh shell

shell.nix

@@ -3,8 +3,9 @@
 pkgs.mkShell {
   buildInputs = with pkgs; [
     # PHP and tools
-    php84
+    (php84.withExtensions ({ enabled, all }: enabled ++ (with all; [ pdo_pgsql pgsql ])))
     php84Packages.composer
+    symfony-cli
 
     # Container tools
     podman
@@ -15,4 +16,9 @@ pkgs.mkShell {
     curl
     gnumake
   ];
+
+  shellHook = ''
+    export SHELL=${pkgs.zsh}/bin/zsh
+    exec ${pkgs.zsh}/bin/zsh
+  '';
 }