Add student birthday tracking with celebration banners and admin notification; v1.1.31

- Admin can set birthday (month/day) per student in Study Users panel
- Summer birthdays (Jun–Aug) prompt admin to set an alternate school-year date
- 🎂 badge on student card header during birthday week
- Dismissible happy birthday banner shown to student on their study hub
- Admin receives email notification on the celebration day, once per year

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/helpers.js

@@ -121,6 +121,51 @@ export function sanitizeRedirectRules(value) {
   return out.length > 0 ? out : DEFAULT_REDIRECT_RULES
 }
 
+// Returns true if the user's celebration date falls within the current Mon–Sun week.
+// Uses birthdayAlternateMonth/Day if set (for summer birthday workarounds), otherwise
+// falls back to birthdayMonth/Day. Checks both the current year and next year so
+// year-wrap birthdays (e.g. Dec 30 checked in late December) work correctly.
+export function isBirthdayThisWeek(user) {
+  const month = user.birthdayMonth
+  const day = user.birthdayDay
+  if (!month || !day) return false
+
+  const celebMonth = user.birthdayAlternateMonth ?? month
+  const celebDay = user.birthdayAlternateDay ?? day
+
+  const today = new Date()
+  const monday = new Date(today)
+  monday.setUTCHours(0, 0, 0, 0)
+  const dow = monday.getUTCDay()
+  monday.setUTCDate(monday.getUTCDate() - (dow === 0 ? 6 : dow - 1))
+  const sunday = new Date(monday)
+  sunday.setUTCDate(sunday.getUTCDate() + 6)
+  sunday.setUTCHours(23, 59, 59, 999)
+
+  const yr = today.getUTCFullYear()
+  for (const year of [yr, yr + 1]) {
+    const bday = new Date(Date.UTC(year, celebMonth - 1, celebDay))
+    if (bday >= monday && bday <= sunday) return true
+  }
+  return false
+}
+
+// June, July, August are considered summer months.
+export function isSummerBirthday(month) {
+  return Number.isInteger(month) && month >= 6 && month <= 8
+}
+
+// Returns "YYYY-MM-DD" for the celebration date (alternate if set, else birthday)
+// in the given year. Returns null if no birthday is set.
+export function celebrationDateForYear(user, year) {
+  const month = user.birthdayMonth
+  const day = user.birthdayDay
+  if (!month || !day) return null
+  const m = user.birthdayAlternateMonth ?? month
+  const d = user.birthdayAlternateDay ?? day
+  return `${year}-${String(m).padStart(2, '0')}-${String(d).padStart(2, '0')}`
+}
+
 export function sanitizeFeaturedLinks(value) {
   const source = Array.isArray(value) ? value : []
   return source