feat: OpsxDB 桌面数据库客户端首版入库

含工作台/连库多引擎字段与 SSH·SSL、结果编辑、Redis 键浏览、
Tauri 桌面与 docs/落地页；排除本地构建产物与 sidecar 二进制。

apps/server/internal/db/open.go

@@ -0,0 +1,85 @@
+package db
+
+import (
+	"database/sql"
+	"fmt"
+	"strings"
+	"time"
+)
+
+func driverKey(d string) string {
+	return strings.ToLower(strings.TrimSpace(d))
+}
+
+func isMySQLFamily(d string) bool {
+	switch driverKey(d) {
+	case "mysql", "mariadb", "tidb", "oceanbase", "polardb", "tdsql":
+		return true
+	default:
+		return false
+	}
+}
+
+func isPostgresFamily(d string) bool {
+	switch driverKey(d) {
+	case "postgresql", "postgres", "gaussdb", "opengauss", "kingbase":
+		return true
+	default:
+		return false
+	}
+}
+
+// Open 按驱动打开 *sql.DB
+func Open(c ConnReq) (*sql.DB, error) {
+	var (
+		db  *sql.DB
+		err error
+	)
+	switch {
+	case isMySQLFamily(c.Driver):
+		db, err = openMySQL(c)
+	case isPostgresFamily(c.Driver):
+		db, err = openPostgres(c)
+	case driverKey(c.Driver) == "sqlserver" || driverKey(c.Driver) == "mssql":
+		db, err = openMSSQL(c)
+	case driverKey(c.Driver) == "oracle":
+		db, err = openOracle(c)
+	case driverKey(c.Driver) == "sqlite":
+		db, err = openSQLite(c)
+	default:
+		return nil, fmt.Errorf("驱动「%s」尚未实现（当前支持: mysql/mariadb/tidb、postgresql、sqlserver、oracle、sqlite、redis）", c.Driver)
+	}
+	if err != nil {
+		return nil, err
+	}
+	db.SetConnMaxLifetime(2 * time.Minute)
+	db.SetMaxOpenConns(5)
+	db.SetMaxIdleConns(2)
+	return db, nil
+}
+
+func TestConnection(c ConnReq) error {
+	dial, tun, err := ApplySSHTunnel(c)
+	if err != nil {
+		return err
+	}
+	if tun != nil {
+		defer tun.Close()
+	}
+	if err := testDial(dial); err != nil {
+		return fmt.Errorf("数据库: %w", err)
+	}
+	return nil
+}
+
+func testDial(c ConnReq) error {
+	if isRedis(c.Driver) {
+		return testRedis(c)
+	}
+	db, err := Open(c)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+	return db.Ping()
+}