fix(mongo): complete agent fallback for all connection paths

- Fix connect_db and test_connection to also fallback to agent when
  native driver fails with wire version error
- Route MongoDB agent through mongo_ops in schema.rs list_databases
- Update MongoDB legacy hint text to mention Driver Manager

src/i18n/locales/en.ts

@@ -179,7 +179,7 @@ export default {
     dmCompatHint: "Requires DM8 ODBC driver installed on your system.",
     dmDownload: "Download from Dameng",
     mongoLegacyHint:
-      "For older MongoDB servers, enter authSource=admin&authMechanism=SCRAM-SHA-1 here; add directConnection=true only when needed for direct standalone connections.",
+      "MongoDB below 4.2 requires the MongoDB (Legacy) driver from Driver Manager; connections will switch automatically.",
     compatible: "Compatible",
     mainstream: "Popular",
     color: "Color",

src/i18n/locales/es.ts

@@ -180,7 +180,7 @@ export default {
     dmCompatHint: "Requiere el driver ODBC DM8 instalado en el sistema.",
     dmDownload: "Descargar desde Dameng",
     mongoLegacyHint:
-      "Para servidores MongoDB más antiguos, ingresa authSource=admin&authMechanism=SCRAM-SHA-1 aquí; agrega directConnection=true solo cuando sea necesario para conexiones directas a instancias independientes.",
+      "MongoDB inferior a 4.2 requiere el controlador MongoDB (Legacy) del Gestor de controladores; la conexión cambiará automáticamente.",
     compatible: "Compatible",
     mainstream: "Popular",
     color: "Color",

src/i18n/locales/zh-CN.ts

@@ -176,8 +176,7 @@ export default {
     jdbcPluginHint: "先安装 DBX JDBC 插件，再导入数据库厂商提供的 JDBC 驱动 JAR。",
     dmCompatHint: "需要在系统上安装达梦 DM8 ODBC 驱动程序。",
     dmDownload: "前往达梦官网下载",
-    mongoLegacyHint:
-      "连接旧版 MongoDB 时，可在此填写 authSource=admin&authMechanism=SCRAM-SHA-1；直连单节点时可按需追加 directConnection=true。",
+    mongoLegacyHint: "MongoDB 4.2 以下版本需在驱动管理中安装 MongoDB (Legacy) 驱动，连接时将自动切换。",
     compatible: "兼容",
     mainstream: "主流",
     color: "颜色",