Move TIME_OPTIONS outside component

- TIME_OPTIONS is now computed at module level, not inside component
- generateTimeOptions now accepts slotDurationMinutes as parameter
- Prevents unnecessary recomputation on every render

frontend/app/admin/availability/page.tsx

@@ -29,7 +29,8 @@ function getDateRange(): Date[] {
 }
 
 // Generate time options for dropdowns (15-min intervals)
-function generateTimeOptions(): string[] {
+// Moved outside component since slotDurationMinutes is a constant
+function generateTimeOptions(slotDurationMinutes: number): string[] {
   const options: string[] = [];
   for (let h = 0; h < 24; h++) {
     for (let m = 0; m < 60; m += slotDurationMinutes) {
@@ -41,7 +42,7 @@ function generateTimeOptions(): string[] {
   return options;
 }
 
-const TIME_OPTIONS = generateTimeOptions();
+const TIME_OPTIONS = generateTimeOptions(slotDurationMinutes);
 
 interface EditSlot {
   start_time: string;