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/routes/admin-assets.js

@@ -1,6 +1,6 @@
 import { mkdir, stat, unlink, writeFile } from 'node:fs/promises'
 import path from 'node:path'
-import { inferImageExtensionFromDataUrl, normalizeAssetBaseName } from '../helpers.js'
+import { inferImageExtensionFromDataUrl, normalizeAssetBaseName, isBirthdayThisWeek } from '../helpers.js'
 import { requireAdminAuth } from '../auth.js'
 import { UPLOADS_DIR } from '../config.js'
 import { state } from '../state.js'
@@ -132,6 +132,11 @@ export function register(app) {
         noteCount,
         subscribeNewsletter: user.subscribeNewsletter !== false,
         studyRemindersEnabled: user.studyRemindersEnabled === true,
+        birthdayMonth: user.birthdayMonth ?? null,
+        birthdayDay: user.birthdayDay ?? null,
+        birthdayAlternateMonth: user.birthdayAlternateMonth ?? null,
+        birthdayAlternateDay: user.birthdayAlternateDay ?? null,
+        isBirthdayWeek: isBirthdayThisWeek(user),
       }
     }))
 
@@ -142,7 +147,7 @@ export function register(app) {
     const user = state.studyUsers.find(u => u.id === req.params.id)
     if (!user) { res.status(404).json({ message: 'User not found.' }); return }
 
-    const { displayName, newPassword, addEnrollment, removeEnrollment } = req.body ?? {}
+    const { displayName, newPassword, addEnrollment, removeEnrollment, birthdayMonth, birthdayDay, birthdayAlternateMonth, birthdayAlternateDay } = req.body ?? {}
 
     if (typeof displayName === 'string') {
       user.displayName = displayName.trim().slice(0, 80)
@@ -172,6 +177,28 @@ export function register(app) {
       user.enrolledStudySlugs = (user.enrolledStudySlugs ?? []).filter(s => s !== slug)
     }
 
+    if (birthdayMonth !== undefined) {
+      const m = parseInt(birthdayMonth, 10)
+      user.birthdayMonth = (Number.isInteger(m) && m >= 1 && m <= 12) ? m : null
+    }
+    if (birthdayDay !== undefined) {
+      const d = parseInt(birthdayDay, 10)
+      user.birthdayDay = (Number.isInteger(d) && d >= 1 && d <= 31) ? d : null
+    }
+    if (birthdayAlternateMonth !== undefined) {
+      const m = parseInt(birthdayAlternateMonth, 10)
+      user.birthdayAlternateMonth = (Number.isInteger(m) && m >= 1 && m <= 12) ? m : null
+      if (!user.birthdayAlternateMonth) user.birthdayAlternateDay = null
+    }
+    if (birthdayAlternateDay !== undefined) {
+      const d = parseInt(birthdayAlternateDay, 10)
+      user.birthdayAlternateDay = (Number.isInteger(d) && d >= 1 && d <= 31) ? d : null
+    }
+    // Clear the sent-year so a changed birthday can trigger a new notification
+    if (birthdayMonth !== undefined || birthdayDay !== undefined || birthdayAlternateMonth !== undefined || birthdayAlternateDay !== undefined) {
+      user.birthdayEmailSentYear = null
+    }
+
     user.updatedAt = new Date().toISOString()
     queueStudyUsersWrite()
     res.json({ ok: true, displayName: user.displayName, enrolledStudySlugs: user.enrolledStudySlugs })