Refactor calendar datasource architecture

Centralizes date calculation logic into DateColumnDataSource
Improves separation of concerns across rendering components

Key changes:
- Introduces IColumnInfo interface for flexible column data
- Moves date calculation from multiple managers to dedicated datasource
- Removes duplicate date rendering logic
- Prepares architecture for future resource-based views

src/managers/NavigationManager.ts

@@ -191,12 +191,12 @@ export class NavigationManager {
     console.log('Calling GridRenderer instead of NavigationRenderer');
     console.log('Target week:', targetWeek);
 
-    // Update DataSource with target week and get dates
+    // Update DataSource with target week and get columns
     this.dataSource.setCurrentDate(targetWeek);
-    const dates = this.dataSource.getColumns();
+    const columns = this.dataSource.getColumns();
 
     // Always create a fresh container for consistent behavior
-    newGrid = this.gridRenderer.createNavigationGrid(container, dates);
+    newGrid = this.gridRenderer.createNavigationGrid(container, columns);
 
     console.groupEnd();