Implement i18next for language switching in the header, enhance task and financial schemas, and add BudgetPlanner.tsx. Replit-Commit-Author: Agent Replit-Commit-Session-Id: ff0be73b-afdd-4747-978b-bb8301fb0a82 Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/9777c70b-fc38-4831-8d6b-78dfffe041b0/012e00c6-f380-4e55-bcb9-10f9adbfbb7b.jpg