Adds month view design and styling

Introduces basic month view structure and styling with week numbers.

Creates expanded month view with event details and duration-based sizing.

Moves event color handling to CSS classes for better flexibility and theming.

src/renderers/HeaderRenderer.ts

@@ -102,7 +102,8 @@ export class DateHeaderRenderer implements HeaderRenderer {
         const gridColumnStart = startColumnIndex + 1;
         const gridColumnEnd = endColumnIndex + 2;
         allDayEvent.style.gridColumn = `${gridColumnStart} / ${gridColumnEnd}`;
-        allDayEvent.style.backgroundColor = event.metadata?.color || '#ff9800';
+        // Color is now handled by CSS classes based on event type
+        allDayEvent.dataset.type = event.type || 'work';
         
         calendarHeader.appendChild(allDayEvent);
       }