fix: correct JSON struct tags in ProgressData

Fix incorrect struct tags for Page, TotalPages, and PageY fields.
Previously used 'int' tag instead of proper JSON field names,
which would cause serialization issues.

internal/sync/progress.go

@@ -14,9 +14,9 @@ type ProgressData struct {
 	Chapter         *int     `json:"chapter,omitempty"`
 	ChapterProgress *float64 `json:"chapter_progress,omitempty"`
 	ViewportY       *float64 `json:"viewport_y,omitempty"`
-	Page            *int     `int,omitempty"`
-	TotalPages      *int     `int,omitempty"`
-	PageY           *int     `int,omitempty"`
+	Page            *int     `json:"page,omitempty"`
+	TotalPages      *int     `json:"total_pages,omitempty"`
+	PageY           *int     `json:"page_y,omitempty"`
 	Zoom            *float64 `json:"zoom,omitempty"`
 	ScrollX         *float64 `json:"scroll_x,omitempty"`
 	ScrollY         *float64 `json:"scroll_y,omitempty"`