feat(shopping): add +page.server.ts with load function and form actions

Load function fetches shopping list and week plan for the current week.
Form actions: check (toggle item), addItem (custom item), generate
(planner-only shopping list generation).

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

frontend/src/routes/(app)/shopping/+page.server.ts

@@ -0,0 +1,86 @@
+import type { PageServerLoad, Actions } from './$types';
+import { apiClient } from '$lib/server/api';
+import { getWeekStart } from '$lib/planner/week';
+
+export const load: PageServerLoad = async ({ fetch, url }) => {
+	const weekParam = url.searchParams.get('week');
+	const weekStart = weekParam ?? getWeekStart(new Date());
+
+	const api = apiClient(fetch);
+
+	const [shoppingResult, weekPlanResult] = await Promise.all([
+		api.GET('/v1/shopping-list', {
+			params: { query: { weekStart } }
+		}),
+		api.GET('/v1/week-plans', {
+			params: { query: { weekStart } }
+		})
+	]);
+
+	return {
+		shoppingList: shoppingResult.data ?? null,
+		weekPlan: weekPlanResult.data ?? null,
+		weekStart
+	};
+};
+
+export const actions: Actions = {
+	check: async ({ fetch, request }) => {
+		const formData = await request.formData();
+		const listId = formData.get('listId') as string;
+		const itemId = formData.get('itemId') as string;
+		const isChecked = formData.get('isChecked') === 'true';
+
+		const api = apiClient(fetch);
+		const { data, error } = await api.PATCH('/v1/shopping-lists/{listId}/items/{itemId}', {
+			params: { path: { listId, itemId } },
+			body: { isChecked }
+		});
+
+		if (error || !data) {
+			return { success: false, error: 'Status konnte nicht geändert werden.' };
+		}
+
+		return { success: true, item: data };
+	},
+
+	addItem: async ({ fetch, request }) => {
+		const formData = await request.formData();
+		const listId = formData.get('listId') as string;
+		const customName = formData.get('customName') as string;
+		const quantity = parseFloat(formData.get('quantity') as string) || 1;
+		const unit = (formData.get('unit') as string) ?? '';
+
+		const api = apiClient(fetch);
+		const { data, error } = await api.POST('/v1/shopping-lists/{id}/items', {
+			params: { path: { id: listId } },
+			body: { customName, quantity, unit }
+		});
+
+		if (error || !data) {
+			return { success: false, error: 'Artikel konnte nicht hinzugefügt werden.' };
+		}
+
+		return { success: true, item: data };
+	},
+
+	generate: async ({ fetch, request, locals }) => {
+		if (locals.benutzer?.rolle !== 'planer') {
+			return { success: false, error: 'Keine Berechtigung.' };
+		}
+
+		const formData = await request.formData();
+		const weekPlanId = formData.get('weekPlanId') as string;
+
+		const api = apiClient(fetch);
+		const { data, error } = await api.POST('/v1/week-plans/{id}/shopping-list', {
+			params: { path: { id: weekPlanId } }
+		});
+
+		if (error || !data) {
+			return { success: false, error: 'Einkaufsliste konnte nicht erstellt werden.' };
+		}
+
+		return { success: true };
+	}
+};