feat: wrap duckdb in devshell with init script

shell.nix

@@ -9,7 +9,11 @@ pkgs.mkShell {
   packages = [
     pkgs.git-lfs
     pkgs.git-xet
-    pkgs.duckdb
+    (pkgs.writeShellScriptBin "duckdb" ''
+      exec ${pkgs.duckdb}/bin/duckdb \
+        -init "${./duckdb/init.sql}" \
+        "$@"
+    '')
     (pkgs.python313.withPackages (ps: [
       ps.duckdb
       ps.matplotlib