improvement: appointment dialog UX improved.

frontend/src/components/appointments/appointmentTime.ts

@@ -61,3 +61,22 @@ export function compareLocalDayStart(a: Date, b: Date): number {
   const tb = new Date(b.getFullYear(), b.getMonth(), b.getDate()).getTime();
   return ta - tb;
 }
+
+export function parseTimeInputToMinutes(time: string): number {
+  const [h, m] = time.split(':').map(Number);
+  if (!Number.isFinite(h) || !Number.isFinite(m)) {
+    return 0;
+  }
+  return h * 60 + m;
+}
+
+export function minutesToTimeInput(minutes: number): string {
+  const clamped = Math.max(0, Math.min(24 * 60 - 1, minutes));
+  const h = Math.floor(clamped / 60);
+  const m = clamped % 60;
+  return `${String(h).padStart(2, '0')}:${String(m).padStart(2, '0')}`;
+}
+
+export function adjustTimeInput(time: string, deltaMinutes: number): string {
+  return minutesToTimeInput(parseTimeInputToMinutes(time) + deltaMinutes);
+}