Správa používateľov + notifikačný systém

- Pridaná kompletná správa používateľov (CRUD, reset hesla, zmena roly) pre ROOT/ADMIN
- Backend: POST /users endpoint, createUser controller, validácia
- Frontend: UserManagement, UserForm, PasswordResetModal komponenty
- Settings prístupné pre ROOT aj ADMIN (AdminRoute)
- Notifikačný systém s snooze funkcionalitou
- Aktualizácia HELPDESK_INIT_V2.md dokumentácie

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

backend/prisma/schema.prisma

@@ -67,6 +67,7 @@ model User {
   taskAttachments    TaskAttachment[]    @relation("TaskAttachmentUploader")
 
   createdCustomers   Customer[]
+  notifications      Notification[]
 
   @@index([email])
   @@index([roleId])
@@ -374,11 +375,12 @@ model Task {
   createdById String
   createdBy   User        @relation("TaskCreator", fields: [createdById], references: [id])
 
-  assignees   TaskAssignee[]
-  reminders   Reminder[]
-  comments    Comment[]
-  tags        TaskTag[]
-  attachments TaskAttachment[]
+  assignees     TaskAssignee[]
+  reminders     Reminder[]
+  comments      Comment[]
+  tags          TaskTag[]
+  attachments   TaskAttachment[]
+  notifications Notification[]
 
   @@index([projectId])
   @@index([parentId])
@@ -633,6 +635,7 @@ model RMA {
   statusHistory   RMAStatusHistory[]
   comments        RMAComment[]
   tags            RMATag[]
+  notifications   Notification[]
 
   @@index([rmaNumber])
   @@index([customerId])
@@ -706,6 +709,40 @@ model RMATag {
   @@id([rmaId, tagId])
 }
 
+// ==================== NOTIFICATIONS ====================
+
+model Notification {
+  id          String    @id @default(cuid())
+
+  userId      String
+  user        User      @relation(fields: [userId], references: [id], onDelete: Cascade)
+
+  type        String    // TASK_ASSIGNED, TASK_STATUS_CHANGED, TASK_COMMENT, TASK_DEADLINE, RMA_ASSIGNED, etc.
+
+  taskId      String?
+  task        Task?     @relation(fields: [taskId], references: [id], onDelete: Cascade)
+
+  rmaId       String?
+  rma         RMA?      @relation(fields: [rmaId], references: [id], onDelete: Cascade)
+
+  title       String
+  message     String
+  data        Json?     // Extra data (oldStatus, newStatus, etc.)
+
+  isRead      Boolean   @default(false)
+  readAt      DateTime?
+
+  snoozedUntil DateTime?
+
+  createdAt   DateTime  @default(now())
+
+  @@index([userId])
+  @@index([userId, isRead])
+  @@index([taskId])
+  @@index([rmaId])
+  @@index([createdAt])
+}
+
 // ==================== ACTIVITY LOG ====================
 
 model ActivityLog {