feat: add upload policies, daily limits, and storage quotas

- Add environment variables to configure anonymous uploads, daily upload caps, and default user storage limits.
- Update config loader to parse and validate the new settings.
- Implement backend logic to track daily usage and active storage per user.
- Update README and `.env.example` to document the new settings and admin panels.

backend/libs/services/upload_test.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 )
 
 func TestDeleteTokenVerification(t *testing.T) {
@@ -59,6 +60,39 @@ func TestDeleteBoxWithTokenRemovesMetadataAndFiles(t *testing.T) {
 	}
 }
 
+func TestUserActiveStorageUsedIgnoresExpiredBoxes(t *testing.T) {
+	service := newTestUploadService(t)
+	active, err := service.CreateBox(testFileHeaders(t, "file", "active.txt", "active"), UploadOptions{MaxDays: 1, OwnerID: "user-1"})
+	if err != nil {
+		t.Fatalf("CreateBox active returned error: %v", err)
+	}
+	expired, err := service.CreateBox(testFileHeaders(t, "file", "expired.txt", "expired"), UploadOptions{MaxDays: 1, OwnerID: "user-1"})
+	if err != nil {
+		t.Fatalf("CreateBox expired returned error: %v", err)
+	}
+	expiredBox, err := service.GetBox(expired.BoxID)
+	if err != nil {
+		t.Fatalf("GetBox returned error: %v", err)
+	}
+	expiredBox.ExpiresAt = time.Now().UTC().Add(-time.Hour)
+	if err := service.SaveBox(expiredBox); err != nil {
+		t.Fatalf("SaveBox returned error: %v", err)
+	}
+
+	activeBox, err := service.GetBox(active.BoxID)
+	if err != nil {
+		t.Fatalf("GetBox active returned error: %v", err)
+	}
+	want := activeBox.Files[0].Size
+	got, err := service.UserActiveStorageUsed("user-1")
+	if err != nil {
+		t.Fatalf("UserActiveStorageUsed returned error: %v", err)
+	}
+	if got != want {
+		t.Fatalf("UserActiveStorageUsed = %d, want %d", got, want)
+	}
+}
+
 func newTestUploadService(t *testing.T) *UploadService {
 	t.Helper()
 	service, err := NewUploadService(1024*1024, t.TempDir(), "http://example.test", slog.New(slog.NewTextHandler(io.Discard, nil)))