feat(upload): add resumable chunk configuration and file validation

- Add `WARPBOX_RESUMABLE_CHUNK_MODE` and `WARPBOX_RESUMABLE_CHUNK_PATH` environment variables to configure temporary chunk storage.
- Implement strict file validation for resuming uploads to ensure selected files match the pending session's metadata.
- Add `PLANS.md` to document development stages, roadmap, and API specifications (including batching and resumable flows).

backend/libs/services/settings.go

@@ -37,6 +37,11 @@ type UploadPolicySettings struct {
 	ShortWindowSeconds      int     `json:"shortWindowSeconds"`
 	AnonymousStorageBackend string  `json:"anonymousStorageBackend"`
 	UserStorageBackend      string  `json:"userStorageBackend"`
+	ResumableUploadsEnabled bool    `json:"resumableUploadsEnabled"`
+	ResumableChunkSizeMB    float64 `json:"resumableChunkSizeMb"`
+	ResumableRetentionHours int     `json:"resumableRetentionHours"`
+	ResumableChunkMode      string  `json:"resumableChunkMode"`
+	ResumableChunkPath      string  `json:"resumableChunkPath"`
 }
 
 type UsageRecord struct {
@@ -89,6 +94,11 @@ func NewSettingsService(db *bbolt.DB, defaults config.SettingsDefaults) (*Settin
 			ShortWindowSeconds:      defaults.ShortWindowSeconds,
 			AnonymousStorageBackend: defaults.AnonymousStorageBackend,
 			UserStorageBackend:      defaults.UserStorageBackend,
+			ResumableUploadsEnabled: defaults.ResumableUploadsEnabled,
+			ResumableChunkSizeMB:    defaults.ResumableChunkSizeMB,
+			ResumableRetentionHours: defaults.ResumableRetentionHours,
+			ResumableChunkMode:      defaults.ResumableChunkMode,
+			ResumableChunkPath:      defaults.ResumableChunkPath,
 		},
 	}
 	service.defaults = service.withBuiltinDefaultGaps(service.defaults)
@@ -143,6 +153,15 @@ func (s *SettingsService) withBuiltinDefaultGaps(settings UploadPolicySettings)
 	if strings.TrimSpace(settings.UserStorageBackend) == "" {
 		settings.UserStorageBackend = StorageBackendLocal
 	}
+	if settings.ResumableChunkSizeMB <= 0 {
+		settings.ResumableChunkSizeMB = 8
+	}
+	if settings.ResumableRetentionHours <= 0 {
+		settings.ResumableRetentionHours = 24
+	}
+	if strings.TrimSpace(settings.ResumableChunkMode) == "" {
+		settings.ResumableChunkMode = "same"
+	}
 	return settings
 }
 
@@ -156,6 +175,13 @@ func (s *SettingsService) UploadPolicy() (UploadPolicySettings, error) {
 		if err := json.Unmarshal(data, &settings); err != nil {
 			return err
 		}
+		var raw map[string]json.RawMessage
+		if err := json.Unmarshal(data, &raw); err != nil {
+			return err
+		}
+		if _, ok := raw["resumableUploadsEnabled"]; !ok {
+			settings.ResumableUploadsEnabled = s.defaults.ResumableUploadsEnabled
+		}
 		settings = s.withDefaultGaps(settings)
 		return nil
 	})
@@ -217,6 +243,15 @@ func (s *SettingsService) withDefaultGaps(settings UploadPolicySettings) UploadP
 	if strings.TrimSpace(settings.UserStorageBackend) == "" {
 		settings.UserStorageBackend = s.defaults.UserStorageBackend
 	}
+	if settings.ResumableChunkSizeMB <= 0 {
+		settings.ResumableChunkSizeMB = s.defaults.ResumableChunkSizeMB
+	}
+	if settings.ResumableRetentionHours <= 0 {
+		settings.ResumableRetentionHours = s.defaults.ResumableRetentionHours
+	}
+	if strings.TrimSpace(settings.ResumableChunkMode) == "" {
+		settings.ResumableChunkMode = s.defaults.ResumableChunkMode
+	}
 	return settings
 }
 
@@ -422,6 +457,18 @@ func (s *SettingsService) validate(settings UploadPolicySettings) error {
 	if settings.ShortWindowRequests <= 0 || settings.ShortWindowSeconds <= 0 {
 		return fmt.Errorf("short-window rate limits must be positive")
 	}
+	if settings.ResumableChunkSizeMB <= 0 {
+		return fmt.Errorf("resumable chunk size must be positive")
+	}
+	if settings.ResumableRetentionHours <= 0 {
+		return fmt.Errorf("resumable retention must be positive")
+	}
+	if settings.ResumableChunkMode != "same" && settings.ResumableChunkMode != "custom" {
+		return fmt.Errorf("resumable chunk storage mode is invalid")
+	}
+	if settings.ResumableChunkMode == "custom" && strings.TrimSpace(settings.ResumableChunkPath) == "" {
+		return fmt.Errorf("custom resumable chunk path is required")
+	}
 	return nil
 }