🐛 fix(vastbase): 修复含点表名误识别为模式 (#757)

- 对含点号或双引号的 PostgreSQL-like 标识符进行可逆引用
- 让 Vastbase 表列表复用统一的 PostgreSQL 元数据解析
- 增加含点表名保持标识符边界的回归测试

Refs #757

internal/db/postgres_impl.go

@@ -379,9 +379,9 @@ func parsePostgresTableNames(data []map[string]interface{}) []string {
 		if name == "" {
 			continue
 		}
-		table := name
+		table := encodePGLikeQualifiedNamePart(name)
 		if schema != "" {
-			table = fmt.Sprintf("%s.%s", schema, name)
+			table = fmt.Sprintf("%s.%s", encodePGLikeQualifiedNamePart(schema), table)
 		}
 		key := strings.ToLower(table)
 		if _, exists := seen[key]; exists {
@@ -393,6 +393,13 @@ func parsePostgresTableNames(data []map[string]interface{}) []string {
 	return tables
 }
 
+func encodePGLikeQualifiedNamePart(identifier string) string {
+	if !strings.ContainsAny(identifier, `."`) {
+		return identifier
+	}
+	return `"` + strings.ReplaceAll(identifier, `"`, `""`) + `"`
+}
+
 func (p *PostgresDB) GetCreateStatement(dbName, tableName string) (string, error) {
 	return fmt.Sprintf("-- SHOW CREATE TABLE not fully supported for PostgreSQL in this MVP.\n-- Table: %s", tableName), nil
 }