feat(scheduling,admin,today): week-range queries, file size limits, mobile nav UX

- Expand exceptional application query to Monday of start week
- Add 20MB file size limit with visual feedback in ImageUpload
- Reorder admin nav links, add burger badge, slide transition + backdrop
- Fetch week-range working/available hours, add closing time indicator
- Skip lunch protection for days <= 5h via shouldApplyLunchProtection
- Extract formatDateISO to shared utils

frontend/src/lib/utils/format.ts

@@ -42,6 +42,15 @@ export function formatDateTime(date: Date | string): string {
 	return `${dateStr} at ${timeStr}`;
 }
 
+/**
+ * Format a Date to ISO date string "YYYY-MM-DD".
+ *
+ * Example: new Date(2026, 4, 29) → "2026-05-29"
+ */
+export function formatDateISO(d: Date): string {
+	return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`;
+}
+
 /**
  * Format a date value to "Weekday, Month Day" only (no time).
  *