Fix banned user login spinner by using config admin_email

[GonzaloGM]

Summary

• Fixes production login error handling for banned and inactive users where $t('usuarioBanneado') threw a vue-i18n SyntaxError on @@ in hardcoded email strings, leaving the login button spinner stuck.
• Replaces hardcoded contact emails in login i18n copy with {adminEmail} interpolation sourced from config.admin_email.
• Adds loginContactMessages helpers and hardens the login error handler with try/finally so loading state always resets.

Test plan

• npm run test:unit -- --run src/utils/loginContactMessages.test.js src/components/views/Login.view.test.js
• npx playwright test e2e-frontend/login.spec.js
• npm run lint
• npm run build:web
• Backend AuthControllerApiTest (no backend changes; verified still passing)
• Manual: attempt login with a banned user in production-like build and confirm deactivated-account message shows with configured admin email