feat: export meal plan to a calendar (.ics) file

Hand-rolled a minimal RFC 5545 writer (lib/ics.ts) rather than adding
a dependency for what's a handful of VEVENTs. Meal slots have no
stored time-of-day, so each mealType maps to a conventional wall-clock
time (dinner 7pm, etc.) written as floating local time, not pinned to
a timezone. Authenticated-only download for now, not a subscribe URL
— that would need a new unguessable-link mechanism on meal plans,
which don't have one today (unlike shopping lists' isPublic).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/app/(app)/meal-plan/page.tsx

@@ -1,7 +1,7 @@
 import type { Metadata } from "next";
 import { headers } from "next/headers";
 import Link from "next/link";
-import { ChevronLeft, ChevronRight, ShoppingCart, Printer } from "lucide-react";
+import { ChevronLeft, ChevronRight, ShoppingCart, Printer, CalendarDays } from "lucide-react";
 import { auth } from "@/lib/auth/server";
 import { db, mealPlans, mealPlanMembers, recipes, userNutritionGoals, eq, and, desc } from "@epicure/db";
 import { buttonVariants } from "@/components/ui/button";
@@ -133,6 +133,10 @@ export default async function MealPlanPage({
             markdown={mealPlanToMarkdown({ label, entries })}
             filename={`meal-plan-${weekStart}`}
           />
+          <a href={`/api/v1/meal-plans/${weekStart}/export/ics`} className={cn(buttonVariants({ variant: "outline", size: "sm" }))}>
+            <CalendarDays className="h-4 w-4" />
+            {msgs.mealPlan.exportCalendar}
+          </a>
           <Link href={`/meal-plan?week=${prevWeek}`} className={cn(buttonVariants({ variant: "outline", size: "sm" }))}>
             <ChevronLeft className="h-4 w-4" />
           </Link>

apps/web/app/api/v1/meal-plans/[weekStart]/export/ics/route.ts

@@ -0,0 +1,59 @@
+import { NextRequest, NextResponse } from "next/server";
+import { db, mealPlans, eq, and } from "@epicure/db";
+import { requireSession } from "@/lib/api-auth";
+import { buildIcs, type IcsEvent } from "@/lib/ics";
+
+type Params = { params: Promise<{ weekStart: string }> };
+
+const DAY_OFFSET: Record<string, number> = { mon: 0, tue: 1, wed: 2, thu: 3, fri: 4, sat: 5, sun: 6 };
+
+// No stored time-of-day for a meal slot, so each mealType gets a
+// conventional wall-clock time and a rough duration for the calendar block.
+const MEAL_TIME: Record<string, { hour: number; minute: number; durationMinutes: number }> = {
+  breakfast: { hour: 8, minute: 0, durationMinutes: 30 },
+  lunch: { hour: 12, minute: 30, durationMinutes: 45 },
+  dinner: { hour: 19, minute: 0, durationMinutes: 60 },
+  snack: { hour: 15, minute: 30, durationMinutes: 15 },
+};
+
+export async function GET(_req: NextRequest, { params }: Params) {
+  const { session, response } = await requireSession();
+  if (response) return response;
+  const { weekStart } = await params;
+
+  const [y, m, d] = weekStart.split("-").map(Number);
+  if (!y || !m || !d) return NextResponse.json({ error: "Invalid weekStart" }, { status: 400 });
+  const monday = new Date(y, m - 1, d);
+
+  const plan = await db.query.mealPlans.findFirst({
+    where: and(eq(mealPlans.userId, session!.user.id), eq(mealPlans.weekStart, weekStart)),
+    with: { entries: { with: { recipe: true, batchDish: true } } },
+  });
+
+  const events: IcsEvent[] = (plan?.entries ?? []).flatMap((entry) => {
+    const title = entry.batchDish?.name ?? entry.recipe?.title;
+    if (!title) return [];
+    const offset = DAY_OFFSET[entry.day] ?? 0;
+    const time = MEAL_TIME[entry.mealType] ?? MEAL_TIME["dinner"]!;
+    const start = new Date(monday);
+    start.setDate(start.getDate() + offset);
+    start.setHours(time.hour, time.minute, 0, 0);
+
+    return [{
+      uid: `epicure-meal-${entry.id}@epicure`,
+      title: `${title} (${entry.mealType})`,
+      description: entry.note ?? undefined,
+      start,
+      durationMinutes: time.durationMinutes,
+    }];
+  });
+
+  const ics = buildIcs(`Epicure meal plan — week of ${weekStart}`, events);
+
+  return new NextResponse(ics, {
+    headers: {
+      "Content-Type": "text/calendar; charset=utf-8",
+      "Content-Disposition": `attachment; filename="meal-plan-${weekStart}.ics"`,
+    },
+  });
+}