feat(admin): wire Admin Users management (A9)

User list with create dialog, role toggle, (de)activate, and reset-password;
self-lockout guard. Adds getUser/resetPassword endpoints, an isActive field on
the User type, and en/ru strings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/api/types.ts

@@ -181,6 +181,7 @@ export interface User {
   username: string;
   email?: string;
   role: 'admin' | 'user';
+  isActive: boolean;
   createdAt: string;
   lastActiveAt?: string;
 }