Prepare product layout and reusable Flutter theme

Relocate the existing Astro website and preserve its assets and hosting configuration. Add the consumer/backend scaffold and themed Flutter package with consumer tests. Related to #1.

website/src/styles/tokens.css

@@ -0,0 +1,17 @@
+/* Generated by npm run tokens. Edit design/tokens.json. */
+:root {
+  --ink: #14221d;
+  --mint: #c4f9ce;
+  --lime: #d7ff5f;
+  --paper: #f9faf6;
+  --muted: #637168;
+  --line: #d9e0d8;
+  --forest: #396a4b;
+  --focus: #168850;
+  --dark-field: #25372e;
+  --dark-receive: #203d2d;
+  --sage-surface: #eaf0e6;
+  --blue-surface: #edf0f9;
+  --radius: 24px;
+  --font-family: 'Onest', Arial, sans-serif;
+}