restructure: flatten workspace nesting, move devcontainer to root

- backend/workspaces/backend/ → backend/
- backend/workspaces/frontend/ → frontend/
- backend/.devcontainer/ + .vscode/ → repo root (where VS Code expects them)
- loose scripts/SQL files → scripts/
- replace nested git repo with single repo at project root
- update docker-compose.yml build context and devcontainer.json path
- add root .gitignore

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/svelte.config.js

@@ -0,0 +1,12 @@
+import adapter from '@sveltejs/adapter-node';
+import { vitePreprocess } from '@sveltejs/vite-plugin-svelte';
+
+/** @type {import('@sveltejs/kit').Config} */
+const config = {
+	// Consult https://svelte.dev/docs/kit/integrations
+	// for more information about preprocessors
+	preprocess: vitePreprocess(),
+	kit: { adapter: adapter() }
+};
+
+export default config;