feat(uploads): add native resumable upload support

Implement a native chunked resumable upload API and frontend integration
to support reliable large file uploads.

Changes include:
- Added a 3-step resumable upload API flow (create session, upload chunks, complete session).
- Introduced configuration options for chunk size, retention hours, and toggling the feature.
- Updated the frontend to utilize resumable uploads with progress tracking.
- Configured temporary chunk storage under `data/tmp/uploads` with automatic cleanup.
- Documented the API flow and configuration in the README.

backend/libs/jobs/cleanup.go

@@ -22,6 +22,14 @@ func newCleanupJob(cfg config.Config, logger *slog.Logger, uploadService *servic
 			if cleaned > 0 {
 				logger.Info("cleanup job complete", "source", "housekeeping", "severity", "user_activity", "code", 2202, "cleaned", cleaned)
 			}
+			cleanedUploads, err := uploadService.CleanupExpiredResumableSessions(time.Now().UTC())
+			if err != nil {
+				logger.Warn("resumable upload cleanup failed", "source", "housekeeping", "severity", "warn", "code", 4204, "error", err.Error())
+				return
+			}
+			if cleanedUploads > 0 {
+				logger.Info("resumable uploads cleaned", "source", "housekeeping", "severity", "user_activity", "code", 2204, "cleaned", cleanedUploads)
+			}
 			if banService != nil {
 				cleanedEvents, err := banService.CleanupAbuseEvents(time.Now().UTC())
 				if err != nil {
@@ -37,7 +45,12 @@ func newCleanupJob(cfg config.Config, logger *slog.Logger, uploadService *servic
 }
 
 func RunCleanupNow(uploadService *services.UploadService, logger *slog.Logger) (int, error) {
-	return cleanupUnavailableBoxes(uploadService, logger)
+	cleaned, err := cleanupUnavailableBoxes(uploadService, logger)
+	if err != nil {
+		return cleaned, err
+	}
+	cleanedUploads, err := uploadService.CleanupExpiredResumableSessions(time.Now().UTC())
+	return cleaned + cleanedUploads, err
 }
 
 func cleanupUnavailableBoxes(uploadService *services.UploadService, logger *slog.Logger) (int, error) {