feat : add User CRUD with admin management

Add User API operations (GET, POST, PATCH, DELETE) with password
hashing processor, frontend service, drawer and admin tab.

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

frontend/services/dto/user-data.ts

@@ -1,5 +1,12 @@
 export type UserData = {
-  id: number
-  username: string
-  roles: string[]
+    id: number
+    '@id'?: string
+    username: string
+    roles: string[]
+}
+
+export type UserWrite = {
+    username: string
+    password?: string
+    roles: string[]
 }