feat: add durable document indexing pipeline

backend/src/kbqa/lifecycle.py

@@ -1,12 +1,18 @@
 from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
 from pathlib import Path
+import asyncio
 
 from fastapi import FastAPI
 from pymilvus import MilvusClient
 
 from kbqa.config import get_settings
 from kbqa.database import Database
+from kbqa.documents.service import DocumentService
+from kbqa.indexing.worker import IndexWorker
+from kbqa.rag.embeddings import EmbeddingProvider
+from kbqa.rag.retriever import KnowledgeRetriever
+from kbqa.rag.vector_store import MilvusVectorStore
 
 
 def _ensure_runtime_directories(database_url: str, milvus_uri: str, raw_data_dir: Path) -> None:
@@ -28,11 +34,30 @@ async def lifespan(app: FastAPI) -> AsyncIterator[None]:
     )
     database = Database(settings.database_url)
     milvus_client = MilvusClient(uri=settings.milvus_uri)
+    vector_store = MilvusVectorStore(milvus_client, settings.embedding_dim)
+    await asyncio.to_thread(vector_store.ensure_collection)
+    embeddings = EmbeddingProvider(settings)
+    retriever = KnowledgeRetriever(embeddings, vector_store, database.session_factory)
+    worker = IndexWorker(settings, database.session_factory, embeddings, vector_store)
+    document_service = DocumentService(
+        settings,
+        database.session_factory,
+        worker,
+        vector_store,
+    )
     app.state.settings = settings
     app.state.database = database
     app.state.milvus_client = milvus_client
+    app.state.vector_store = vector_store
+    app.state.embeddings = embeddings
+    app.state.retriever = retriever
+    app.state.index_worker = worker
+    app.state.document_service = document_service
+    await worker.start()
+    await document_service.recover_deletions()
     try:
         yield
     finally:
+        await worker.stop()
         milvus_client.close()
         await database.dispose()