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/postgres.go

@@ -0,0 +1,147 @@
+package db
+
+import (
+	"database/sql"
+	"fmt"
+	"strings"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+)
+
+func openPostgres(c ConnReq) (*sql.DB, error) {
+	host := c.Host
+	if host == "" {
+		host = "127.0.0.1"
+	}
+	port := c.Port
+	if port == 0 {
+		port = 5432
+	}
+	user := c.User
+	if user == "" {
+		user = "postgres"
+	}
+	dbName := c.Database
+	if dbName == "" {
+		dbName = "postgres"
+	}
+	mode := EffectiveSSLMode(c)
+	sslmode := "disable"
+	switch mode {
+	case "disable":
+		sslmode = "disable"
+	case "require", "skip-verify":
+		// libpq require ≈ encrypt without CA/hostname verify
+		sslmode = "require"
+	case "verify-ca":
+		sslmode = "verify-ca"
+		if strings.TrimSpace(c.SSLCA) == "" {
+			return nil, fmt.Errorf("verify-ca 模式需要填写 CA 证书路径")
+		}
+	default:
+		return nil, fmt.Errorf("未知 SSL 模式: %s", mode)
+	}
+
+	var b strings.Builder
+	fmt.Fprintf(&b, "host=%s port=%d user=%s password=%s dbname=%s sslmode=%s connect_timeout=5",
+		pqEscape(host), port, pqEscape(user), pqEscape(c.Password), pqEscape(dbName), sslmode)
+	if ca := strings.TrimSpace(c.SSLCA); ca != "" {
+		fmt.Fprintf(&b, " sslrootcert=%s", pqEscape(ca))
+	}
+	if cert := strings.TrimSpace(c.SSLCert); cert != "" {
+		fmt.Fprintf(&b, " sslcert=%s", pqEscape(cert))
+	}
+	if key := strings.TrimSpace(c.SSLKey); key != "" {
+		fmt.Fprintf(&b, " sslkey=%s", pqEscape(key))
+	}
+	return sql.Open("pgx", b.String())
+}
+
+func pqEscape(v string) string {
+	if v == "" {
+		return "''"
+	}
+	needs := strings.ContainsAny(v, " '\\")
+	if !needs {
+		return v
+	}
+	return "'" + strings.ReplaceAll(strings.ReplaceAll(v, `\`, `\\`), `'`, `\'`) + "'"
+}
+
+func listDatabasesPostgres(db *sql.DB) ([]string, error) {
+	rows, err := db.Query(`SELECT datname FROM pg_database WHERE datistemplate = false ORDER BY 1`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []string
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			return nil, err
+		}
+		out = append(out, name)
+	}
+	return out, rows.Err()
+}
+
+func listTablesPostgres(db *sql.DB, database string) ([]string, error) {
+	// 当前连接库下的 public 表；切库需重新 Open
+	_ = database
+	rows, err := db.Query(`
+		SELECT CASE WHEN schemaname = 'public' THEN tablename ELSE schemaname || '.' || tablename END
+		FROM pg_catalog.pg_tables
+		WHERE schemaname NOT IN ('pg_catalog','information_schema')
+		ORDER BY 1`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []string
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			return nil, err
+		}
+		out = append(out, name)
+	}
+	return out, rows.Err()
+}
+
+func listColumnsPostgres(dbh *sql.DB, _, table string) ([]ColumnInfo, error) {
+	schema, t := splitSchemaTable(table)
+	if schema == "" {
+		schema = "public"
+	}
+	rows, err := dbh.Query(`
+		SELECT column_name, data_type,
+			COALESCE(character_maximum_length::text, numeric_precision::text, ''),
+			is_nullable, column_default
+		FROM information_schema.columns
+		WHERE table_schema = $1 AND table_name = $2
+		ORDER BY ordinal_position`, schema, t)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []ColumnInfo
+	for rows.Next() {
+		var name, typ, extra, nullable string
+		var def sql.NullString
+		if err := rows.Scan(&name, &typ, &extra, &nullable, &def); err != nil {
+			return nil, err
+		}
+		if extra != "" {
+			typ = typ + "(" + extra + ")"
+		}
+		col := ColumnInfo{Name: name, Type: typ, Nullable: nullable == "YES"}
+		if def.Valid {
+			col.Default = def.String
+		}
+		out = append(out, col)
+	}
+	if out == nil {
+		out = []ColumnInfo{}
+	}
+	return out, rows.Err()
+}