feat(database): support configurable SSL mode for PostgreSQL and MySQL

Add ssl_mode configuration option to allow users to customize SSL/TLS
policy for database connections instead of hardcoding sslmode=disable
for PostgreSQL and having no TLS support for MySQL.

Changes:
- database.Config, DatabaseConfig: add SSLMode field
- PostgreSQL DSN: replace hardcoded sslmode=disable with configurable
value
- MySQL DSN: append &tls=<SSLMode> parameter when SSLMode is set
- Full config pipeline: INI/env -> DatabaseConfig -> Config -> DSN ->
subprocess
- New env var BH_DB_SSL_MODE and ini key [database] ssl_mode
- Updated config example and documentation

internal/bootstrap/bootstrap.go

@@ -107,6 +107,7 @@ func (a *App) initDatabase() {
 		DBName:   a.Config.Database.DBName,
 		Path:     a.Config.Database.Path,
 		DSN:      a.Config.Database.DSN,
+		SSLMode:  a.Config.Database.SSLMode,
 	}
 
 	if err := database.Init(dbCfg); err != nil {