Wire frontend into Docker Compose with type-safe API client

- Add frontend service to docker-compose.yml (port 3000, BACKEND_URL env var)
- Add frontend/Dockerfile using adapter-node for plain Node/Docker runtime
- Switch svelte.config.js from adapter-auto to adapter-node
- Generate OpenAPI types from backend spec (openapi-typescript + openapi-fetch)
- Add src/lib/server/api.ts as server-only typed API client factory
- Add generate:api script to regenerate types when backend spec changes

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

frontend/src/lib/server/api.ts

@@ -0,0 +1,19 @@
+import createClient from 'openapi-fetch';
+import type { paths } from '$lib/api/schema.d.ts';
+import { env } from '$env/dynamic/private';
+
+// Usage in +page.server.ts load functions and form actions:
+//
+//   export const load = async ({ fetch }) => {
+//     const api = apiClient(fetch);
+//     const { data, error } = await api.GET('/v1/recipes', { ... });
+//   };
+//
+// Always pass SvelteKit's `fetch` so session cookies are forwarded correctly.
+
+export function apiClient(fetch?: typeof globalThis.fetch) {
+	return createClient<paths>({
+		baseUrl: env.BACKEND_URL ?? 'http://localhost:8080',
+		fetch: fetch ?? globalThis.fetch
+	});
+}