feat: wire GraphRAG API handlers, activities, and database layer

internal/api/server.go

@@ -74,6 +74,22 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			s.api.ExecuteWorkflow(w, r, parts[2])
 		}
 
+	// GraphRAG query endpoint
+	case strings.HasSuffix(path, "/query") && method == http.MethodPost:
+		// POST /workflows/{id}/query
+		parts := strings.Split(path, "/")
+		if len(parts) >= 4 && parts[1] == "workflows" && parts[3] == "query" {
+			s.api.QueryWorkflowGraph(w, r, parts[2])
+		}
+
+	// Relation versions endpoint
+	case strings.Contains(path, "/relations/") && strings.Contains(path, "/versions") && method == http.MethodGet:
+		// GET /workflows/{id}/relations/{edge_id}/versions
+		parts := strings.Split(path, "/")
+		if len(parts) >= 6 && parts[1] == "workflows" && parts[3] == "relations" && parts[5] == "versions" {
+			s.api.GetWorkflowRelationVersions(w, r, parts[2], parts[4])
+		}
+
 	// Execution endpoints
 	case strings.HasPrefix(path, "/executions/") && method == http.MethodGet:
 		id := extractID(path, "/executions/")