- Add Config struct with server, database, Redis, IMSI, and ES2+ settings
- Add ServerConfig with port and timeout settings (30s read/write)
- Add DatabaseConfig for PostgreSQL connection parameters
- Add RedisConfig for cache connection settings
- Add IMSIConfig with France MCC+MNC prefix (20893) and IMSI range
- Add ES2Config for eSIM provisioning with SMDP connection parameters
- Add LoadConfig function with default configuration values
- Include JSON