feat(direnv): migrate .dev to envrc use_dev

direnv/direnv.toml

@@ -0,0 +1,2 @@
+[global]
+hide_env_diff = true

direnv/lib/use_dev.sh

@@ -0,0 +1,7 @@
+# composable nix devshell from matej.nix
+# usage in .envrc: use dev uv_14 pg_18
+use_dev() {
+  for component in "$@"; do
+    use flake "dev#${component}"
+  done
+}