Add Autosend node with Mail and Contact resources

Implement n8n node for Autosend API with support for:
- Mail resource: Send single and bulk emails with template or custom content
- Contact resource: Create/update contacts (upsert) and get contacts by ID or email
- API key authentication
- Declarative routing following n8n best practices
- Full TypeScript support with proper typing
- Passing all linting checks

nodes/Autosend/resources/mail/index.ts

@@ -0,0 +1,46 @@
+import type { INodeProperties } from 'n8n-workflow';
+import { sendOperation } from './send';
+import { sendBulkOperation } from './sendBulk';
+
+export const mailOperations: INodeProperties[] = [
+	{
+		displayName: 'Operation',
+		name: 'operation',
+		type: 'options',
+		noDataExpression: true,
+		displayOptions: {
+			show: {
+				resource: ['mail'],
+			},
+		},
+		options: [
+			{
+				name: 'Send',
+				value: 'send',
+				description: 'Send a single email',
+				action: 'Send an email',
+				routing: {
+					request: {
+						method: 'POST',
+						url: '/mails/send',
+					},
+				},
+			},
+			{
+				name: 'Send Bulk',
+				value: 'sendBulk',
+				description: 'Send emails to multiple recipients',
+				action: 'Send bulk emails',
+				routing: {
+					request: {
+						method: 'POST',
+						url: '/mails/bulk',
+					},
+				},
+			},
+		],
+		default: 'send',
+	},
+];
+
+export const mailFields: INodeProperties[] = [...sendOperation, ...sendBulkOperation];