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/app/webapp.go

@@ -8,6 +8,7 @@ import (
 	"github.com/dhao2001/mygo/internal/config"
 	"github.com/dhao2001/mygo/internal/repository"
 	"github.com/dhao2001/mygo/internal/service"
+	"github.com/dhao2001/mygo/internal/storage"
 )
 
 // WebApp contains application-wide runtime dependencies and metadata.
@@ -21,6 +22,8 @@ type WebApp struct {
 	FileRepo       repository.FileRepository
 	CredentialRepo repository.CredentialRepository
 	AuthService    *service.AuthService
+	FileService    *service.FileService
+	Storage        storage.StorageBackend
 }
 
 // Bootstrap creates a fully initialized WebApp from config.
@@ -48,6 +51,13 @@ func Bootstrap(cfg *config.Config) (*WebApp, error) {
 		cfg.JWT.RefreshTTL,
 	)
 
+	store, err := storage.NewLocalStorage(cfg.Storage.Local.Path)
+	if err != nil {
+		return nil, fmt.Errorf("init storage: %w", err)
+	}
+
+	fileService := service.NewFileService(fileRepo, store, cfg.Storage.MaxUploadSize)
+
 	return &WebApp{
 		Config:         cfg,
 		Version:        AppVersion,
@@ -57,6 +67,8 @@ func Bootstrap(cfg *config.Config) (*WebApp, error) {
 		FileRepo:       fileRepo,
 		CredentialRepo: credentialRepo,
 		AuthService:    authService,
+		FileService:    fileService,
+		Storage:        store,
 	}, nil
 }
 
@@ -67,6 +79,8 @@ func NewWebApp(cfg *config.Config, db *gorm.DB,
 	fileRepo repository.FileRepository,
 	credentialRepo repository.CredentialRepository,
 	authService *service.AuthService,
+	fileService *service.FileService,
+	store storage.StorageBackend,
 ) *WebApp {
 	return &WebApp{
 		Config:         cfg,
@@ -77,6 +91,8 @@ func NewWebApp(cfg *config.Config, db *gorm.DB,
 		FileRepo:       fileRepo,
 		CredentialRepo: credentialRepo,
 		AuthService:    authService,
+		FileService:    fileService,
+		Storage:        store,
 	}
 }