flake.nix: decouple devShell

devShell.nix

@@ -0,0 +1,28 @@
+{ pkgs }:
+pkgs.mkShell {
+  packages = with pkgs; [
+    (fenix.stable.withComponents [
+      "cargo"
+      "clippy"
+      "rust-src"
+      "rustc"
+      "rustfmt"
+      "rust-analyzer"
+    ])
+    gcc
+    openssl
+    pkg-config
+
+    nodejs
+    biome
+
+    sqlite
+    sqlx-cli
+    lazysql
+
+    claude-code
+
+    typos
+    tokei
+  ];
+}