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/utils/runtime_env.go

@@ -35,6 +35,7 @@ func BuildRuntimeProcessEnv() []string {
 	appendEnvIfSet(&envs, "BH_DB_PATH", constant.RuntimeDBPath)
 	appendEnvIfSet(&envs, "BH_DB_DSN", constant.RuntimeDBDSN)
 	appendEnvIfSet(&envs, "BH_DB_TABLE_PREFIX", constant.RuntimeDBTablePrefix)
+	appendEnvIfSet(&envs, "BH_DB_SSL_MODE", constant.RuntimeDBSSLMode)
 
 	return envs
 }