feat: add knowledge retrieval service

backend/apps/knowledge/tests/test_retrieval.py

@@ -0,0 +1,53 @@
+from apps.knowledge.models import KnowledgeBase, KnowledgeChunk, KnowledgeItem
+from apps.knowledge.services import retrieve_knowledge
+from apps.solutions.models import Solution
+
+
+def test_retrieve_knowledge_prefers_relevant_chunk(db):
+    base = KnowledgeBase.objects.create(name="采集知识库", scope="数据采集")
+    item = KnowledgeItem.objects.create(
+        knowledge_base=base,
+        title="税局采集进度",
+        problem="采集进度不更新",
+        solution="查询 Python 日志，确认税局状态。",
+        status="published",
+    )
+    KnowledgeChunk.objects.create(
+        knowledge_base=base,
+        item=item,
+        chunk_index=0,
+        content="税局采集进度不更新时，需要查询 Python 日志。",
+        embedding=[0.1, 0.2],
+        metadata={"source_type": "knowledge_item", "title": item.title},
+    )
+    KnowledgeChunk.objects.create(
+        knowledge_base=base,
+        chunk_index=1,
+        content="登录失败通常需要检查账号密码。",
+        embedding=[0.9, 0.1],
+        metadata={"source_type": "document", "title": "登录问题"},
+    )
+
+    results = retrieve_knowledge("税局采集进度怎么查询", limit=1)
+
+    assert len(results) == 1
+    assert results[0]["title"] == "税局采集进度"
+    assert "Python 日志" in results[0]["content"]
+
+
+def test_published_solution_can_be_indexed_for_retrieval(db):
+    solution = Solution.objects.create(
+        title="税局不稳定采集处理中",
+        problem_signature="采集进度长时间不更新",
+        root_cause="税局服务不稳定",
+        solution="回复客户税局不稳定，任务仍在采集中。",
+        status="published",
+    )
+
+    from apps.knowledge.services import index_published_solution
+
+    chunks = index_published_solution(solution)
+
+    assert len(chunks) == 1
+    assert chunks[0].metadata["source_type"] == "solution"
+    assert chunks[0].metadata["solution_id"] == solution.id