feat: 1-to-1 message render + web data-lake backend

frontend/src/lib/format/datetime.ts

@@ -0,0 +1,39 @@
+const time = new Intl.DateTimeFormat(undefined, {
+  hour: "2-digit",
+  minute: "2-digit",
+});
+const day = new Intl.DateTimeFormat(undefined, {
+  day: "numeric",
+  month: "short",
+});
+const full = new Intl.DateTimeFormat(undefined, {
+  day: "numeric",
+  month: "short",
+  year: "numeric",
+  hour: "2-digit",
+  minute: "2-digit",
+});
+
+export function formatTime(iso: string): string {
+  return time.format(new Date(iso));
+}
+
+export function formatDay(iso: string): string {
+  return day.format(new Date(iso));
+}
+
+export function formatFull(iso: string): string {
+  return full.format(new Date(iso));
+}
+
+export function formatListDate(iso: string | null): string {
+  if (!iso) {
+    return "";
+  }
+  const date = new Date(iso);
+  const now = new Date();
+  if (date.toDateString() === now.toDateString()) {
+    return time.format(date);
+  }
+  return day.format(date);
+}