Add file management API with local storage backend

- Implement FileHandler with CRUD operations for files/directories
- Add FileService with business logic and SHA-256 hashing
- Create LocalStorage backend for filesystem persistence
- Add database repository with pagination and name uniqueness
  constraints
- Configure max upload size in storage settings
- Include comprehensive tests for all layers

internal/handler/account_test.go

@@ -14,12 +14,6 @@ import (
 	"github.com/dhao2001/mygo/internal/service"
 )
 
-func setupAccountHandler(t *testing.T) (*AccountHandler, []byte) {
-	t.Helper()
-	svc, secret := setupTestAuthService(t)
-	return NewAccountHandler(svc), secret
-}
-
 func setupAccountRouter(t *testing.T) (*gin.Engine, []byte) {
 	t.Helper()