refactor: extract shared formatting utilities (duration, date, age)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

frontend/src/lib/utils/format.ts

@@ -0,0 +1,88 @@
+/**
+ * Shared formatting utilities for consistent display across the app.
+ */
+
+/**
+ * Convert minutes to a human-readable duration string.
+ *
+ * Examples:
+ *   45   → "45m"
+ *   60   → "1h"
+ *   90   → "1h 30m"
+ *   120  → "2h"
+ *   150  → "2h 30m"
+ */
+export function formatDuration(minutes: number): string {
+	const hours = Math.floor(minutes / 60);
+	const mins = minutes % 60;
+	if (hours === 0) return `${mins}m`;
+	if (mins === 0) return `${hours}h`;
+	return `${hours}h ${mins}m`;
+}
+
+/**
+ * Format a date/time to "Weekday, Month Day at HH:MM AM/PM".
+ *
+ * Examples:
+ *   "2026-05-29T10:00:00Z" → "Friday, May 29 at 10:00 AM"
+ *   "2026-06-05T14:30:00Z" → "Friday, Jun 5 at 2:30 PM"
+ */
+export function formatDateTime(date: Date | string): string {
+	const d = typeof date === 'string' ? new Date(date) : date;
+	const dateStr = d.toLocaleDateString('en-US', {
+		weekday: 'long',
+		month: 'short',
+		day: 'numeric'
+	});
+	const timeStr = d.toLocaleTimeString('en-US', {
+		hour: 'numeric',
+		minute: '2-digit',
+		hour12: true
+	});
+	return `${dateStr} at ${timeStr}`;
+}
+
+/**
+ * Format a date value to "Weekday, Month Day" only (no time).
+ *
+ * Example: "2026-05-29" → "Friday, May 29"
+ */
+export function formatDate(date: Date | string): string {
+	const d = typeof date === 'string' ? new Date(date) : date;
+	return d.toLocaleDateString('en-US', {
+		weekday: 'long',
+		month: 'short',
+		day: 'numeric'
+	});
+}
+
+/**
+ * Format a time value to "HH:MM AM/PM".
+ *
+ * Example:  new Date("2026-05-29T14:30:00Z") → "2:30 PM"
+ */
+export function formatTime(date: Date | string): string {
+	const d = typeof date === 'string' ? new Date(date) : date;
+	return d.toLocaleTimeString('en-US', {
+		hour: 'numeric',
+		minute: '2-digit',
+		hour12: true
+	});
+}
+
+/**
+ * Calculate age from a date-of-birth string.
+ * Returns the number of full years, or null if DOB is invalid.
+ */
+export function calculateAge(dateOfBirth: string | undefined | null): number | null {
+	if (!dateOfBirth) return null;
+	const dob = new Date(dateOfBirth);
+	if (isNaN(dob.getTime())) return null;
+	const today = new Date();
+	let age = today.getFullYear() - dob.getFullYear();
+	const monthDiff = today.getMonth() - dob.getMonth();
+	if (monthDiff < 0 || (monthDiff === 0 && today.getDate() < dob.getDate())) {
+		age--;
+	}
+	return age;
+}