feat: add Exotel webhook controller and service for call event parsing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app.module.ts

@@ -2,6 +2,7 @@ import { Module } from '@nestjs/common';
 import { ConfigModule } from '@nestjs/config';
 import configuration from './config/configuration';
 import { PlatformModule } from './platform/platform.module';
+import { ExotelModule } from './exotel/exotel.module';
 
 @Module({
     imports: [
@@ -10,6 +11,7 @@ import { PlatformModule } from './platform/platform.module';
             isGlobal: true,
         }),
         PlatformModule,
+        ExotelModule,
     ],
 })
 export class AppModule {}