Add educator email invitations and staff notification preferences

prisma/schema.prisma

@@ -213,6 +213,7 @@ model User {
   privacyPolicyVersion    String?
   /// Zeitstempel des Opt-Ins für das interne Kita-Adressbuch (Modul 3).
   directoryOptInAt        DateTime?
+  staffDecisionEmails     Boolean   @default(true)
 
   // Auth-Bookkeeping
   emailVerifiedAt     DateTime?
@@ -243,6 +244,7 @@ model User {
   auditLogsAuthored  AuditLog[]          @relation("AuditLogActor")
   staffProfile       StaffProfile?
   staffNotifications StaffNotification[]
+  staffEmails        StaffEmail[]
 
   @@index([kitaId])
   @@index([familyId])
@@ -348,11 +350,35 @@ model StaffProfile {
   adjustments     StaffAdjustment[]
   history         StaffHistory[]
   notifications   StaffNotification[]
+  emails          StaffEmail[]
 
   @@index([kitaId])
   @@map("staff_profiles")
 }
 
+// Persisted in the same transaction as the staff action; delivered after commit.
+model StaffEmail {
+  id          String       @id @default(cuid())
+  profileId   String
+  profile     StaffProfile @relation(fields: [profileId], references: [id], onDelete: Cascade)
+  userId      String
+  user        User         @relation(fields: [userId], references: [id], onDelete: Cascade)
+  toAdmins    Boolean      @default(false)
+  subject     String
+  message     String
+  path        String
+  inviteToken String?
+  createdAt   DateTime     @default(now())
+  sentAt      DateTime?
+  skippedAt   DateTime?
+  leaseUntil  DateTime?
+  attempts    Int          @default(0)
+  failed      Boolean      @default(false)
+
+  @@index([profileId, sentAt, skippedAt])
+  @@map("staff_emails")
+}
+
 model StaffWorkPattern {
   id            String       @id @default(cuid())
   profileId     String