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/server/routes_protected.go

@@ -11,6 +11,7 @@ import (
 func setupProtectedRoutes(rg *gin.RouterGroup, webApp *app.WebApp) {
 	jwtSecret := []byte(webApp.Config.JWT.Secret)
 	accountHandler := handler.NewAccountHandler(webApp.AuthService)
+	fileHandler := handler.NewFileHandler(webApp.FileService)
 
 	rg.Use(middleware.AuthRequired(jwtSecret))
 
@@ -25,4 +26,14 @@ func setupProtectedRoutes(rg *gin.RouterGroup, webApp *app.WebApp) {
 			passkeys.DELETE("/:id", accountHandler.RevokePasskey)
 		}
 	}
+
+	files := rg.Group("/files")
+	{
+		files.GET("", fileHandler.List)
+		files.POST("", fileHandler.Upload)
+		files.GET("/:id", fileHandler.Get)
+		files.GET("/:id/content", fileHandler.Download)
+		files.PUT("/:id", fileHandler.Update)
+		files.DELETE("/:id", fileHandler.Delete)
+	}
 }