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.

.vscode/launch.json

@@ -2,7 +2,8 @@
   "version": "0.2.0",
   "configurations": [
     {
-      "command": "./node_modules/.bin/astro dev",
+      "command": "npm run dev -- --background",
+      "cwd": "${workspaceFolder}/website",
       "name": "Development server",
       "request": "launch",
       "type": "node-terminal"