feat(planner): add RecipePicker component (C4) and suggestions API endpoint

C4 sheet content: Empfohlen section with variety delta badges,
Alle Rezepte with client-side search filter. GET /planner endpoint
proxies suggestions to backend for lazy client-side loading.

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

frontend/src/routes/(app)/planner/+server.ts

@@ -0,0 +1,24 @@
+import { json } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { apiClient } from '$lib/server/api';
+
+// GET /planner?planId=&date= — returns suggestions JSON for C4 recipe picker
+export const GET: RequestHandler = async ({ fetch, url }) => {
+	const planId = url.searchParams.get('planId');
+	const date = url.searchParams.get('date');
+
+	if (!planId || !date) {
+		return json({ suggestions: [] });
+	}
+
+	const api = apiClient(fetch);
+	const { data } = await api.GET('/v1/week-plans/{id}/suggestions', {
+		params: { path: { id: planId }, query: { slotDate: date } }
+	});
+
+	const suggestions = (data?.suggestions ?? []).sort(
+		(a: any, b: any) => (b.simulatedScore ?? 0) - (a.simulatedScore ?? 0)
+	);
+
+	return json({ suggestions });
+};