feat(planner): implement C1 weekly planner home screen (#26)

Three-breakpoint layout (mobile/tablet/desktop) with VarietyScoreCard,
WeekStrip, DayMealCard components. Server loads week plan and variety
score via API; read-only role behavior derived from benutzer.rolle.

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

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

@@ -0,0 +1,45 @@
+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 { data: weekPlan, error } = await api.GET('/v1/week-plans', {
+		params: { query: { weekStart } }
+	});
+
+	if (error || !weekPlan?.id) {
+		return { weekPlan: null, varietyScore: null, weekStart };
+	}
+
+	const { data: varietyScore } = await api.GET('/v1/week-plans/{id}/variety-score', {
+		params: { path: { id: weekPlan.id } }
+	});
+
+	return {
+		weekPlan,
+		varietyScore: varietyScore ?? null,
+		weekStart
+	};
+};
+
+export const actions: Actions = {
+	createPlan: async ({ fetch, request }) => {
+		const formData = await request.formData();
+		const weekStart = formData.get('weekStart') as string;
+
+		const api = apiClient(fetch);
+		const { data, error } = await api.POST('/v1/week-plans', {
+			body: { weekStart }
+		});
+
+		if (error || !data) {
+			return { success: false, error: 'Plan konnte nicht erstellt werden.' };
+		}
+
+		return { success: true };
+	}
+};