refactor(server): use boxstore helpers and file status consts

- Move box ID validation, file listing/pathing, manifest creation, and uploads to `boxstore`
- Use shared helpers for safe filenames and polling interval env parsing
- Add file status constants to `models` to avoid duplicated magic strings across handlersrefactor(server): use boxstore helpers and file status consts

- Move box ID validation, file listing/pathing, manifest creation, and uploads to `boxstore`
- Use shared helpers for safe filenames and polling interval env parsing
- Add file status constants to `models` to avoid duplicated magic strings across handlers

lib/models/models.go

@@ -1,5 +1,12 @@
 package models
 
+const (
+	FileStatusFailed = "failed"
+	FileStatusReady  = "complete"
+	FileStatusWait   = "pending"
+	FileStatusWork   = "uploading"
+)
+
 type BoxFile struct {
 	ID           string `json:"id"`
 	Name         string `json:"name"`