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/study-auth.js

@@ -6,7 +6,7 @@ import {
   verifyTotpCode,
   generateRecoveryCodes,
 } from '../auth.js'
-import { parseCookies } from '../helpers.js'
+import { parseCookies, isBirthdayThisWeek } from '../helpers.js'
 import { STUDY_SESSION_COOKIE, MAX_STUDY_USERS, MAX_CONTACT_SUBMISSIONS } from '../config.js'
 import { state } from '../state.js'
 import {
@@ -57,6 +57,7 @@ export function register(app) {
       totpEnabled: Boolean(user && (user.twoFaMethod === 'app' || user.twoFaMethod === 'email') && (user.twoFaMethod === 'email' || (user.totpSecret && user.totpVerified))),
       twoFaMethod: user?.twoFaMethod ?? null,
       totpRecoveryCodesRemaining: user?.twoFaMethod === 'app' ? (user.totpRecoveryCodes?.length ?? 0) : 0,
+      isBirthdayWeek: user ? isBirthdayThisWeek(user) : false,
     })
   })