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/logout/+page.server.ts

@@ -0,0 +1,12 @@
+import { redirect } from '@sveltejs/kit';
+import type { Actions } from './$types';
+
+export const actions = {
+    default: async ({ cookies }) => {
+        // Das Auth-Cookie löschen
+        cookies.delete('auth_token', { path: '/' });
+
+        // Zur Login-Seite werfen
+        throw redirect(302, '/login');
+    }
+} satisfies Actions;