feat: implement RAG Service MVP with PARSER + Memory integration

RAG Service Implementation:
- Create rag-service/ with full structure (config, document_store, embedding, pipelines)
- Document Store: PostgreSQL + pgvector via Haystack
- Embedding: BAAI/bge-m3 (multilingual, 1024 dim)
- Ingest Pipeline: Convert ParsedDocument to Haystack Documents, embed, index
- Query Pipeline: Retrieve documents, generate answers via DAGI Router
- FastAPI endpoints: /ingest, /query, /health

Tests:
- Unit tests for ingest and query pipelines
- E2E test with example parsed JSON
- Test fixtures with real PARSER output example

Router Integration:
- Add mode='rag_query' routing rule in router-config.yml
- Priority 7, uses local_qwen3_8b for RAG queries

Docker:
- Add rag-service to docker-compose.yml
- Configure dependencies (router, city-db)
- Add model cache volume

Documentation:
- Complete README with API examples
- Integration guides for PARSER and Router

services/rag-service/tests/test_query.py

@@ -0,0 +1,50 @@
+"""
+Tests for query pipeline
+"""
+
+import pytest
+from unittest.mock import AsyncMock, patch, MagicMock
+from app.query_pipeline import answer_query, _build_citations
+
+
+class TestQueryPipeline:
+    """Tests for RAG query pipeline"""
+    
+    @pytest.mark.asyncio
+    async def test_answer_query_no_documents(self):
+        """Test query when no documents found"""
+        with patch("app.query_pipeline._retrieve_documents", return_value=[]):
+            result = await answer_query(
+                dao_id="test-dao",
+                question="Test question"
+            )
+            
+            assert "answer" in result
+            assert "На жаль, я не знайшов" in result["answer"]
+            assert result["citations"] == []
+    
+    @pytest.mark.asyncio
+    async def test_build_citations(self):
+        """Test citation building"""
+        from haystack.schema import Document
+        
+        documents = [
+            Document(
+                content="Test content 1",
+                meta={"doc_id": "doc1", "page": 1, "section": "Section 1"}
+            ),
+            Document(
+                content="Test content 2",
+                meta={"doc_id": "doc2", "page": 2}
+            )
+        ]
+        
+        citations = _build_citations(documents)
+        
+        assert len(citations) == 2
+        assert citations[0]["doc_id"] == "doc1"
+        assert citations[0]["page"] == 1
+        assert citations[0]["section"] == "Section 1"
+        assert citations[1]["doc_id"] == "doc2"
+        assert citations[1]["page"] == 2
+