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/lib/changelog.ts

@@ -1,5 +1,5 @@
 // Mirrors CHANGELOG.md at the repo root — update both together.
-export const APP_VERSION = "0.18.0";
+export const APP_VERSION = "0.19.0";
 
 export type ChangelogEntry = {
   version: string;
@@ -11,6 +11,13 @@ export type ChangelogEntry = {
 };
 
 export const CHANGELOG: ChangelogEntry[] = [
+  {
+    version: "0.19.0",
+    date: "2026-07-13 22:21",
+    added: [
+      "**Export your meal plan to a calendar file** — download a week's meals as a .ics file to import into Google/Apple/Outlook calendar.",
+    ],
+  },
   {
     version: "0.18.0",
     date: "2026-07-13 22:16",

apps/web/lib/ics.ts

@@ -0,0 +1,70 @@
+// Minimal hand-rolled iCalendar (RFC 5545) writer — the meal plan only needs
+// a handful of all-day-ish VEVENTs, not enough to justify a dependency.
+
+export type IcsEvent = {
+  uid: string;
+  title: string;
+  description?: string;
+  start: Date;
+  durationMinutes: number;
+};
+
+function foldLine(line: string): string {
+  // RFC 5545 §3.1: lines over 75 octets should be folded with a leading space
+  // on the continuation — not strictly required for readers to work, but
+  // keeps long recipe titles/descriptions spec-compliant.
+  if (line.length <= 75) return line;
+  const chunks: string[] = [];
+  let rest = line;
+  while (rest.length > 75) {
+    chunks.push(rest.slice(0, 75));
+    rest = " " + rest.slice(75);
+  }
+  chunks.push(rest);
+  return chunks.join("\r\n");
+}
+
+function escapeText(text: string): string {
+  return text.replace(/\\/g, "\\\\").replace(/;/g, "\\;").replace(/,/g, "\\,").replace(/\n/g, "\\n");
+}
+
+// Floating local time (no trailing "Z", no UTC conversion) — meal times have
+// no stored timezone, so this is authored as "7pm wherever you're looking at
+// this calendar" rather than pinned to one instant, per RFC 5545 §3.3.5.
+function formatDateTime(d: Date): string {
+  const pad = (n: number) => String(n).padStart(2, "0");
+  return `${d.getFullYear()}${pad(d.getMonth() + 1)}${pad(d.getDate())}T${pad(d.getHours())}${pad(d.getMinutes())}${pad(d.getSeconds())}`;
+}
+
+function formatUtcStamp(d: Date): string {
+  const pad = (n: number) => String(n).padStart(2, "0");
+  return `${d.getUTCFullYear()}${pad(d.getUTCMonth() + 1)}${pad(d.getUTCDate())}T${pad(d.getUTCHours())}${pad(d.getUTCMinutes())}${pad(d.getUTCSeconds())}Z`;
+}
+
+export function buildIcs(calendarName: string, events: IcsEvent[]): string {
+  const now = formatUtcStamp(new Date());
+  const lines: string[] = [
+    "BEGIN:VCALENDAR",
+    "VERSION:2.0",
+    "PRODID:-//Epicure//Meal Plan//EN",
+    "CALSCALE:GREGORIAN",
+    foldLine(`X-WR-CALNAME:${escapeText(calendarName)}`),
+  ];
+
+  for (const event of events) {
+    const end = new Date(event.start.getTime() + event.durationMinutes * 60_000);
+    lines.push(
+      "BEGIN:VEVENT",
+      `UID:${event.uid}`,
+      `DTSTAMP:${now}`,
+      `DTSTART:${formatDateTime(event.start)}`,
+      `DTEND:${formatDateTime(end)}`,
+      foldLine(`SUMMARY:${escapeText(event.title)}`)
+    );
+    if (event.description) lines.push(foldLine(`DESCRIPTION:${escapeText(event.description)}`));
+    lines.push("END:VEVENT");
+  }
+
+  lines.push("END:VCALENDAR");
+  return lines.join("\r\n") + "\r\n";
+}