Remove MSW handlers and update demo credentials for improved standardization

- Deleted `admin.ts`, `auth.ts`, and `users.ts` MSW handler files to streamline demo mode setup.
- Updated demo credentials logic in `DemoCredentialsModal` and `DemoModeBanner` for stronger password requirements (≥12 characters).
- Refined documentation in `CLAUDE.md` to align with new credential standards and auto-generated MSW workflows.

frontend/src/config/app.config.ts

@@ -124,8 +124,8 @@ export const config = {
     enabled: parseBool(ENV.DEMO_MODE, false),
     // Demo credentials
     credentials: {
-      user: { email: 'demo@example.com', password: 'DemoPass123' },
-      admin: { email: 'admin@example.com', password: 'AdminPass123' },
+      user: { email: 'demo@example.com', password: 'DemoPass1234!' },
+      admin: { email: 'admin@example.com', password: 'AdminPass1234!' },
     },
   },