Rebrand to Sage & Cream identity, working contact form, drop Firebase

- New sage/cream palette and stacked logo lockup (The Vine over Coffeehouse
  + Bakery) driven by currentColor; logo SVGs now colorable
- Reuse the logo component for the hero and section marks
- Rewrite site copy: real founding (Morissa Bennett, 2024), real story from
  the product range, remove invented claims and AI phrasing
- Contact form now sends over SMTP via /api/contact (nodemailer) with real
  send/error states, server-side validation, and reply-to the customer;
  delivers to CONTACT_TO. Add .env.example and a test-email script
- Fix mobile: unmount the off-screen menu (killed sideways scroll), cap logo
  width, responsive heroes and type
- Remove Firebase (config, tracked build output, placeholder pages, nix
  firebase-tools) now that hosting has moved
- Delete dead code: LoyaltyCardForm, ProductModal, LoadingSpinner, card-flip
  CSS, unused Playfair font
- Serve dev/start on port 2024

default.nix

@@ -5,14 +5,11 @@ in
 pkgs.mkShell {
   buildInputs = [
     pkgs.nodejs
-    pkgs.yarn
-    pkgs.firebase-tools
   ];
 
-  # Install Next.js via yarn in the shell
   shellHook = ''
     if ! [ -d "node_modules" ]; then
-      yarn add next react react-dom
+      npm install --legacy-peer-deps
     fi
   '';
-}
+}