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)