Implement calendar deletion with right-click context menu

Added complete calendar deletion functionality including:
- Context menu component with right-click activation on calendar items
- Backend API endpoint for calendar deletion with CalDAV DELETE method
- Frontend integration with calendar list refresh after deletion
- Fixed URL construction to prevent double /dav.php path issue
- Added proper error handling and user feedback

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/src/handlers.rs

@@ -7,7 +7,7 @@ use serde::Deserialize;
 use std::sync::Arc;
 use chrono::Datelike;
 
-use crate::{AppState, models::{CalDAVLoginRequest, AuthResponse, ApiError, UserInfo, CalendarInfo, CreateCalendarRequest, CreateCalendarResponse}};
+use crate::{AppState, models::{CalDAVLoginRequest, AuthResponse, ApiError, UserInfo, CalendarInfo, CreateCalendarRequest, CreateCalendarResponse, DeleteCalendarRequest, DeleteCalendarResponse}};
 use crate::calendar::{CalDAVClient, CalendarEvent};
 
 #[derive(Deserialize)]
@@ -292,4 +292,35 @@ pub async fn create_calendar(
         success: true,
         message: "Calendar created successfully".to_string(),
     }))
+}
+
+pub async fn delete_calendar(
+    State(state): State<Arc<AppState>>,
+    headers: HeaderMap,
+    Json(request): Json<DeleteCalendarRequest>,
+) -> Result<Json<DeleteCalendarResponse>, ApiError> {
+    println!("🗑️ Delete calendar request received: path='{}'", request.path);
+    
+    // Extract and verify token
+    let token = extract_bearer_token(&headers)?;
+    let password = extract_password_header(&headers)?;
+
+    // Validate request
+    if request.path.trim().is_empty() {
+        return Err(ApiError::BadRequest("Calendar path is required".to_string()));
+    }
+
+    // Create CalDAV config from token and password
+    let config = state.auth_service.caldav_config_from_token(&token, &password)?;
+    let client = CalDAVClient::new(config);
+
+    // Delete the calendar
+    client.delete_calendar(&request.path)
+        .await
+        .map_err(|e| ApiError::Internal(format!("Failed to delete calendar: {}", e)))?;
+
+    Ok(Json(DeleteCalendarResponse {
+        success: true,
+        message: "Calendar deleted successfully".to_string(),
+    }))
 }