feat: 收敛知识库检索调度与评分语义

- 固定 rag.engine 与 Milvus 配置，补齐启动期检索基础设施校验

- 支持调用方配置 retrievalMode，并统一知识库检索入口与结果来源展示

- 修正关键词检索 knowledgeId 过滤、混合检索评分归一化与本地 ES 默认配置

easyflow-ui-admin/app/src/locales/langs/en-US/bot.json

@@ -49,6 +49,12 @@
   "publicChatCopySuccess": "Copied",
   "publicChatCopyFail": "Copy failed",
   "basicInfo": "Basic Info",
+  "knowledgeRetrievalMode": "Retrieval Mode",
+  "retrievalModes": {
+    "hybrid": "Hybrid Retrieval",
+    "vector": "Vector Retrieval",
+    "keyword": "Keyword Retrieval"
+  },
   "modal": {
     "createDescription": "Set the assistant appearance, identity and base availability.",
     "editDescription": "Update the assistant presentation and base availability.",