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.go

@@ -0,0 +1,25 @@
+package infra
+
+import (
+	"database/sql"
+	"fmt"
+
+	_ "github.com/ClickHouse/clickhouse-go/v2"
+)
+
+// ClickHouseOpen connects to a ClickHouse server and returns a *sql.DB.
+// Constructs a DSN of the form:
+//
+//	clickhouse://user:password@host:port/database
+func ClickHouseOpen(host string, port int, user, password, database string) (*sql.DB, error) {
+	dsn := fmt.Sprintf("clickhouse://%s:%s@%s:%d/%s", user, password, host, port, database)
+	db, err := sql.Open("clickhouse", dsn)
+	if err != nil {
+		return nil, fmt.Errorf("clickhouse_open: open: %w", err)
+	}
+	if err := db.Ping(); err != nil {
+		db.Close()
+		return nil, fmt.Errorf("clickhouse_open: ping %s:%d/%s: %w", host, port, database, err)
+	}
+	return db, nil
+}