security: remove hardcoded cluster.local URLs from source code

- activity/memory.go: read MEMORY_SERVICE_URL from env, default localhost
- pkg/db/db.go: remove cluster.local from DSN comment
- Fix memory_test.go env var name to match

activity/memory.go

@@ -92,9 +92,9 @@ func RetrieveMemoryActivity(ctx context.Context, in RetrieveMemoryInput) (Retrie
 	}
 
 	// Get memory service URL and token
-	baseURL := os.Getenv("POIMEN_MEMORY_URL")
+	baseURL := os.Getenv("MEMORY_SERVICE_URL")
 	if baseURL == "" {
-		baseURL = "http://poimen-memory.poimen.svc.cluster.local:8080"
+		baseURL = "http://localhost:8080"
 	}
 
 	token := os.Getenv("POIMEN_MEMORY_TOKEN")