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/eslint.config.js

@@ -0,0 +1,43 @@
+import prettier from 'eslint-config-prettier';
+import { fileURLToPath } from 'node:url';
+import { includeIgnoreFile } from '@eslint/compat';
+import js from '@eslint/js';
+import svelte from 'eslint-plugin-svelte';
+import { defineConfig } from 'eslint/config';
+import globals from 'globals';
+import ts from 'typescript-eslint';
+import svelteConfig from './svelte.config.js';
+
+const gitignorePath = fileURLToPath(new URL('./.gitignore', import.meta.url));
+
+export default defineConfig(
+	includeIgnoreFile(gitignorePath),
+	js.configs.recommended,
+	...ts.configs.recommended,
+	...svelte.configs.recommended,
+	prettier,
+	...svelte.configs.prettier,
+	{
+		languageOptions: {
+			globals: { ...globals.browser, ...globals.node }
+		},
+		rules: { // typescript-eslint strongly recommend that you do not use the no-undef lint rule on TypeScript projects.
+		// see: https://typescript-eslint.io/troubleshooting/faqs/eslint/#i-get-errors-from-the-no-undef-rule-about-global-variables-not-being-defined-even-though-there-are-no-typescript-errors
+		"no-undef": 'off' }
+	},
+	{
+		files: [
+			'**/*.svelte',
+			'**/*.svelte.ts',
+			'**/*.svelte.js'
+		],
+		languageOptions: {
+			parserOptions: {
+				projectService: true,
+				extraFileExtensions: ['.svelte'],
+				parser: ts.parser,
+				svelteConfig
+			}
+		}
+	}
+);