Integrate sync queue system and device cap API

- Start queue processor as background goroutine
- Initialize and register queue handler
- Add queue management routes (7 endpoints)
- Update KOReader handler to use checkpoint sync mode
- Add device cap management route (PUT /api/auth/users/:id/max-devices)
- Register all new endpoints with proper middleware

cmd/server/main.go

@@ -57,9 +57,14 @@ func main() {
 	connManager := sync.NewConnectionManager()
 	connManager.StartCleanupTask()
 
-	koreaderHandler := handlers.NewKOReaderHandler(queries, connManager)
+	// Create sync queue processor
+	queueProcessor := sync.NewSyncQueueProcessor(queries)
+	go queueProcessor.Start(context.Background())
+
+	koreaderHandler := handlers.NewKOReaderHandler(queries, connManager, queueProcessor)
 	wsHandler := handlers.NewWSHandler(queries, connManager, cfg.JWTSecret, deviceAuthMiddleware)
 	conflictHandler := handlers.NewConflictHandler(queries, connManager)
+	queueHandler := handlers.NewQueueHandler(queries, queueProcessor)
 
 	e := echo.New()
 
@@ -147,6 +152,7 @@ func main() {
 	// Admin-only routes for user and folder management
 	admin := protected.Group("/auth", handlers.AdminMiddleware)
 	admin.GET("/users", authHandler.ListUsers)
+	admin.PUT("/users/:id/max-devices", authHandler.UpdateUserMaxDevices)
 
 	// Library management routes
 	library := protected.Group("/libraries")
@@ -238,6 +244,18 @@ func main() {
 	conflicts.DELETE("/:id", conflictHandler.DeleteConflict)
 	conflicts.POST("/dismiss-all", conflictHandler.DismissAllResolved)
 
+	// Sync queue management routes (protected - require user auth)
+	queue := protected.Group("/queue")
+	queue.GET("/devices/:device_id/stats", queueHandler.GetDeviceQueueStats)
+	queue.GET("/devices/:device_id/items", queueHandler.ListDeviceQueueItems)
+	queue.POST("/items/:item_id/retry", queueHandler.RetryQueueItem)
+	queue.DELETE("/items/:item_id", queueHandler.DeleteQueueItem)
+	queue.DELETE("/devices/:device_id/clear", queueHandler.ClearDeviceQueue)
+
+	// Admin-only queue routes
+	adminQueue := queue.Group("", handlers.AdminMiddleware)
+	adminQueue.GET("/items", queueHandler.ListAllQueueItems)
+
 	// WebSocket endpoint for real-time sync
 	e.GET("/ws/sync", wsHandler.HandleWebSocket)
 

internal/handlers/koreader.go

@@ -17,10 +17,11 @@ import (
 type KOReaderHandler struct {
 	db          *database.Queries
 	connManager *wsync.ConnectionManager
+	queue       *wsync.SyncQueueProcessor
 }
 
-func NewKOReaderHandler(db *database.Queries, connManager *wsync.ConnectionManager) *KOReaderHandler {
-	return &KOReaderHandler{db: db, connManager: connManager}
+func NewKOReaderHandler(db *database.Queries, connManager *wsync.ConnectionManager, queue *wsync.SyncQueueProcessor) *KOReaderHandler {
+	return &KOReaderHandler{db: db, connManager: connManager, queue: queue}
 }
 
 type KOReaderProgressRequest struct {
@@ -168,6 +169,15 @@ func (h *KOReaderHandler) SyncProgress(c echo.Context) error {
 
 	pgUserID := pgtype.UUID{Bytes: userID, Valid: true}
 
+	syncMode := req.SyncMode
+	if syncMode == "" {
+		syncMode = "immediate"
+	}
+
+	if syncMode == "checkpoint" {
+		return h.handleCheckpointSync(c, device, pgUserID, req)
+	}
+
 	booksSynced := 0
 	conflicts := []KOReaderConflict{}
 
@@ -222,7 +232,7 @@ func (h *KOReaderHandler) SyncProgress(c echo.Context) error {
 		})
 	}
 
-	if req.SyncMode == "immediate" {
+	if syncMode == "immediate" {
 		return c.JSON(http.StatusAccepted, KOReaderSyncResponse{
 			SyncStatus:    "accepted",
 			BooksSynced:   booksSynced,
@@ -241,6 +251,90 @@ func (h *KOReaderHandler) SyncProgress(c echo.Context) error {
 	})
 }
 
+func (h *KOReaderHandler) handleCheckpointSync(c echo.Context, device database.Devices, userID pgtype.UUID, req KOReaderProgressRequest) error {
+	booksEnqueued := 0
+
+	for _, book := range req.Books {
+		var mediaUUID uuid.UUID
+		var err error
+
+		if book.UUID != "" {
+			mediaUUID, err = uuid.Parse(book.UUID)
+			if err != nil {
+				continue
+			}
+
+			mediaItem, err := h.db.GetMediaItem(c.Request().Context(), pgtype.UUID{Bytes: mediaUUID, Valid: true})
+			if err == nil {
+				err = h.enqueueProgressForBook(c, device.ID, userID, mediaItem.ID, book)
+				if err == nil {
+					booksEnqueued++
+				}
+			}
+		} else if book.FilePath != "" {
+			mediaItem, err := h.db.GetMediaItemByFilePath(c.Request().Context(), book.FilePath)
+			if err == nil {
+				err = h.enqueueProgressForBook(c, device.ID, userID, mediaItem.ID, book)
+				if err == nil {
+					booksEnqueued++
+				}
+			}
+		} else if book.Title != "" {
+			mediaItems, err := h.db.ListMediaItems(c.Request().Context(), database.ListMediaItemsParams{
+				Limit:  100,
+				Offset: 0,
+			})
+			if err == nil {
+				for _, mi := range mediaItems {
+					if mi.Title == book.Title && (book.Authors == nil || mi.Author.String == book.Authors[0]) {
+						err = h.enqueueProgressForBook(c, device.ID, userID, mi.ID, book)
+						if err == nil {
+							booksEnqueued++
+						}
+						break
+					}
+				}
+			}
+		}
+	}
+
+	_, err := h.db.UpdateDeviceLastSync(c.Request().Context(), device.ID)
+	if err != nil {
+		return c.JSON(http.StatusInternalServerError, map[string]string{
+			"error": "failed to update device timestamp",
+		})
+	}
+
+	return c.JSON(http.StatusAccepted, map[string]interface{}{
+		"sync_status":    "checkpoint_enqueued",
+		"books_enqueued": booksEnqueued,
+		"message":        "Sync will be processed in the background",
+		"timestamp":      time.Now().Format(time.RFC3339),
+	})
+}
+
+func (h *KOReaderHandler) enqueueProgressForBook(c echo.Context, deviceID pgtype.UUID, userID pgtype.UUID, mediaItemID pgtype.UUID, book KOReaderBookProgress) error {
+	if h.queue == nil {
+		return fmt.Errorf("sync queue not available")
+	}
+
+	update := &wsync.ProgressUpdate{
+		DeviceID:    deviceID,
+		MediaItemID: mediaItemID,
+		UserID:      userID,
+		Percentage:  book.Percentage,
+		Epubcfi:     book.Epubcfi,
+		Chapter:     book.Chapter,
+		Character:   book.Character,
+		Page:        book.Page,
+		TotalPages:  book.TotalPages,
+		Source:      "koreader",
+		SyncMode:    "checkpoint",
+	}
+
+	return h.queue.EnqueueProgress(update)
+}
+
 func (h *KOReaderHandler) updateProgressForBook(c echo.Context, userID pgtype.UUID, mediaItemID pgtype.UUID, book KOReaderBookProgress) error {
 	ctx := c.Request().Context()