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/src/routes/demo/+page.svelte

@@ -0,0 +1,5 @@
+<script lang="ts">
+	import { resolve } from '$app/paths';
+</script>
+
+<a href={resolve('/demo/paraglide')}>paraglide</a>

frontend/src/routes/demo/paraglide/+page.svelte

@@ -0,0 +1,17 @@
+<script lang="ts">
+	import { setLocale } from '$lib/paraglide/runtime';
+	import { page } from '$app/state';
+	import { goto } from '$app/navigation';
+	import { m } from '$lib/paraglide/messages.js';
+</script>
+
+
+
+<h1>{m.hello_world({ name: 'SvelteKit User' })}</h1>
+<div>
+	<button onclick={() => setLocale('en')}>en</button>
+	<button onclick={() => setLocale('es')}>es</button>
+	<button onclick={() => setLocale('de')}>de</button>
+</div><p>
+If you use VSCode, install the <a href="https://marketplace.visualstudio.com/items?itemName=inlang.vs-code-extension" target="_blank">Sherlock i18n extension</a> for a better i18n experience.
+</p>