feat(storage): add S3 backend support and advanced upload limits

- Introduce S3-compatible storage backend support using minio-go.
- Add configuration options for local storage limits, box limits, and rate limiting.
- Implement storage backend selection (local vs S3) for anonymous and registered users.
- Add an `/admin/storage` management interface.
- Update documentation and environment examples with the new configuration variables.

backend/libs/config/config.go

@@ -38,6 +38,17 @@ type SettingsDefaults struct {
 	UserDailyUploadMB       float64
 	DefaultUserStorageMB    float64
 	UsageRetentionDays      int
+	LocalStorageMaxGB       float64
+	AnonymousMaxDays        int
+	UserMaxDays             int
+	AnonymousDailyBoxes     int
+	UserDailyBoxes          int
+	AnonymousActiveBoxes    int
+	UserActiveBoxes         int
+	ShortWindowRequests     int
+	ShortWindowSeconds      int
+	AnonymousStorageBackend string
+	UserStorageBackend      string
 }
 
 func Load() (Config, error) {
@@ -66,6 +77,17 @@ func Load() (Config, error) {
 			UserDailyUploadMB:       envMegabytesFloat("WARPBOX_USER_DAILY_UPLOAD_MB", 8192),
 			DefaultUserStorageMB:    envMegabytesFloat("WARPBOX_DEFAULT_USER_STORAGE_MB", 51200),
 			UsageRetentionDays:      envInt("WARPBOX_USAGE_RETENTION_DAYS", 30),
+			LocalStorageMaxGB:       envGigabytesFloat("WARPBOX_LOCAL_STORAGE_MAX_GB", 100),
+			AnonymousMaxDays:        envInt("WARPBOX_ANONYMOUS_MAX_DAYS", 30),
+			UserMaxDays:             envInt("WARPBOX_USER_MAX_DAYS", 90),
+			AnonymousDailyBoxes:     envInt("WARPBOX_ANONYMOUS_DAILY_BOXES", 100),
+			UserDailyBoxes:          envInt("WARPBOX_USER_DAILY_BOXES", 250),
+			AnonymousActiveBoxes:    envInt("WARPBOX_ANONYMOUS_ACTIVE_BOXES", 500),
+			UserActiveBoxes:         envInt("WARPBOX_USER_ACTIVE_BOXES", 1000),
+			ShortWindowRequests:     envInt("WARPBOX_SHORT_WINDOW_REQUESTS", 60),
+			ShortWindowSeconds:      envInt("WARPBOX_SHORT_WINDOW_SECONDS", 60),
+			AnonymousStorageBackend: envString("WARPBOX_ANONYMOUS_STORAGE_BACKEND", "local"),
+			UserStorageBackend:      envString("WARPBOX_USER_STORAGE_BACKEND", "local"),
 		},
 	}
 
@@ -79,7 +101,16 @@ func Load() (Config, error) {
 		cfg.DefaultSettings.AnonymousDailyUploadMB <= 0 ||
 		cfg.DefaultSettings.UserDailyUploadMB <= 0 ||
 		cfg.DefaultSettings.DefaultUserStorageMB <= 0 ||
-		cfg.DefaultSettings.UsageRetentionDays <= 0 {
+		cfg.DefaultSettings.UsageRetentionDays <= 0 ||
+		cfg.DefaultSettings.LocalStorageMaxGB <= 0 ||
+		cfg.DefaultSettings.AnonymousMaxDays <= 0 ||
+		cfg.DefaultSettings.UserMaxDays <= 0 ||
+		cfg.DefaultSettings.AnonymousDailyBoxes <= 0 ||
+		cfg.DefaultSettings.UserDailyBoxes <= 0 ||
+		cfg.DefaultSettings.AnonymousActiveBoxes <= 0 ||
+		cfg.DefaultSettings.UserActiveBoxes <= 0 ||
+		cfg.DefaultSettings.ShortWindowRequests <= 0 ||
+		cfg.DefaultSettings.ShortWindowSeconds <= 0 {
 		return Config{}, fmt.Errorf("upload policy settings must be positive")
 	}
 
@@ -172,6 +203,23 @@ func envMegabytesFloat(key string, fallback float64) float64 {
 	return parsed
 }
 
+func envGigabytesFloat(key string, fallback float64) float64 {
+	value := strings.TrimSpace(os.Getenv(key))
+	if value == "" {
+		return fallback
+	}
+	normalized := strings.TrimSpace(value)
+	normalized = strings.TrimSuffix(normalized, "GB")
+	normalized = strings.TrimSuffix(normalized, "Gb")
+	normalized = strings.TrimSuffix(normalized, "gb")
+	normalized = strings.TrimSpace(normalized)
+	parsed, err := strconv.ParseFloat(normalized, 64)
+	if err != nil || parsed <= 0 {
+		return fallback
+	}
+	return parsed
+}
+
 func parseMegabytes(value string) (int64, error) {
 	sizeMB, err := parseMegabytesFloat(value)
 	if err != nil {