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/documentCollection.json

@@ -159,7 +159,13 @@
   "documentPreview": "DocumentPreview",
   "total": "Total",
   "segments": "Segments",
-  "similarityScore": "SimilarityScore",
+  "similarityScore": "Relevance",
+  "searchFailed": "Search failed. Please try again later.",
+  "hitSources": {
+    "vector": "Vector Hit",
+    "keyword": "Keyword Hit",
+    "both": "Dual Hit"
+  },
   "alibabaCloud": "AlibabaCloud",
   "tencentCloud": "tencentCloud",
   "vectorEmbedModelTips": "After successful vector data, it is not allowed to modify the vector model",