feat: abstracción DB multi-engine — CRUD genérico y openers para SQLite, Postgres, ClickHouse, DuckDB

Funciones Go con interfaz unificada para operaciones DB: open, close, create_table, exec, query, insert_row, insert_batch.
Openers específicos por engine. Tipo DBConfig para configuración común.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

functions/infra/clickhouse_open.md

@@ -0,0 +1,37 @@
+---
+name: clickhouse_open
+kind: function
+lang: go
+domain: infra
+version: "1.0.0"
+purity: impure
+signature: "func ClickHouseOpen(host string, port int, user, password, database string) (*sql.DB, error)"
+description: "Conecta a ClickHouse construyendo DSN clickhouse://user:pass@host:port/database."
+tags: [database, clickhouse, connection, sql, olap]
+uses_functions: []
+uses_types: [db_config_go_infra]
+returns: []
+returns_optional: false
+error_type: "error_go_core"
+imports: ["database/sql", "github.com/ClickHouse/clickhouse-go/v2"]
+tested: false
+tests: []
+test_file_path: ""
+file_path: "functions/infra/clickhouse_open.go"
+---
+
+## Ejemplo
+
+```go
+db, err := ClickHouseOpen("localhost", 9000, "default", "", "analytics")
+if err != nil {
+    log.Fatal(err)
+}
+defer DBClose(db)
+
+rows, err := DBQuery(db, "SELECT event, count() FROM events GROUP BY event")
+```
+
+## Notas
+
+Usa el driver `github.com/ClickHouse/clickhouse-go/v2` registrado como "clickhouse". Puerto por defecto de ClickHouse es 9000 (nativo) o 8123 (HTTP). Hace ping al abrir para verificar conectividad.