refactor(router): update router comments and variable names

- Update comment: 'ebook handler' -> 'scanner handler'
- Rename ebookHandler variable to scannerHandler in router.go
- Update registerProgressRoutes parameter name
- Update registerScannerRoutes calls to use new variable name

internal/router/router.go

@@ -132,15 +132,15 @@ func RegisterRoutes(cfg *Config) *handlers.Handler {
 	registerFrontendRoutes(cfg)
 	registerDocumentationRoutes(cfg)
 
-	// Create ebook handler for scanner routes and progress routes
-	ebookHandler := handlers.SetupRoutes(protected, cfg.Queries, cfg.ConnManager)
+	// Create scanner handler for scanner routes and progress routes
+	scannerHandler := handlers.SetupRoutes(protected, cfg.Queries, cfg.ConnManager)
 
 	// Register progress routes with actual handler
-	registerProgressRoutes(cfg, ebookHandler)
+	registerProgressRoutes(cfg, scannerHandler)
 
 	// Register scanner routes (admin only)
 	admin := protected.Group("", handlers.AdminMiddleware)
-	registerScannerRoutes(admin, ebookHandler)
+	registerScannerRoutes(admin, scannerHandler)
 
-	return ebookHandler
+	return scannerHandler
 }