Implements native scrollbars with styling

Replaces custom scrollbar implementation with native scrollbars for better performance and accessibility.

Adds configuration options for scrollbar styling, including width, color, track color, hover color, and border radius.

Synchronizes week header and time axis scrolling with the scrollable content.

src/core/CalendarConfig.ts

@@ -39,6 +39,13 @@ export class CalendarConfig {
       showWorkHours: true,
       fitToWidth: false,       // Fit columns to calendar width (no horizontal scroll)
       
+      // Scrollbar styling
+      scrollbarWidth: 16,     // Width of scrollbar in pixels
+      scrollbarColor: '#666', // Scrollbar thumb color
+      scrollbarTrackColor: '#f0f0f0', // Scrollbar track color
+      scrollbarHoverColor: '#b53f7aff', // Scrollbar thumb hover color
+      scrollbarBorderRadius: 6, // Border radius for scrollbar thumb
+      
       // Interaction settings
       allowDrag: true,
       allowResize: true,