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/db_create_table.go

@@ -0,0 +1,32 @@
+package infra
+
+import (
+	"database/sql"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+var validIdentifier = regexp.MustCompile(`^[a-zA-Z_][a-zA-Z0-9_]*$`)
+
+// DBCreateTable executes CREATE TABLE IF NOT EXISTS for the given table with
+// the provided column definitions. Each element of columns should be a full
+// SQL column definition, e.g. "id INTEGER PRIMARY KEY" or "name TEXT NOT NULL".
+// Returns an error if the table name contains invalid characters.
+func DBCreateTable(db *sql.DB, table string, columns []string) error {
+	if !validIdentifier.MatchString(table) {
+		return fmt.Errorf("db_create_table: invalid table name %q (only alphanumeric and underscore allowed)", table)
+	}
+	if len(columns) == 0 {
+		return fmt.Errorf("db_create_table: at least one column definition required")
+	}
+	query := fmt.Sprintf(
+		"CREATE TABLE IF NOT EXISTS %s (%s)",
+		table,
+		strings.Join(columns, ", "),
+	)
+	if _, err := db.Exec(query); err != nil {
+		return fmt.Errorf("db_create_table %q: %w", table, err)
+	}
+	return nil
+}