refactor(api): restructured API for type safety, maintainability and docs generation

- These changes makes the API incombatible with previous versions
- Added new types for error handling, success responses, and health checks.
- Updated health check logic to utilize the new types for better clarity and structure.
- Refactored existing handlers to improve response consistency and error handling.
- Updated Makefile to include a new target for generating API types from Swagger.
- Updated "new agent" API to respond an encrypted cert pair

internal/jsonstore/jsonstore.go

@@ -51,6 +51,11 @@ func init() {
 func loadNS[T store](ns namespace) T {
 	store := reflect.New(reflect.TypeFor[T]().Elem()).Interface().(T)
 	store.Initialize()
+
+	if common.IsTest {
+		return store
+	}
+
 	path := filepath.Join(storesPath, string(ns)+".json")
 	file, err := os.Open(path)
 	if err != nil {