test: add scripts for local bot handler testing and database migration verification

feat: implement key-less FX service with native CBSL web scraping and fallback cache logic

feat: add database connectivity test script for Supabase PostgreSQL instance

feat: add script to verify asynchronous database connection to Supabase

security: Remove hardcoded telegram bot tokens from tracked source files

feat: implement FX service with persistent caching and optimize concurrent rate fetching in main

feat: add test scripts for Telegram bot functionality and webhook integration