chore: scaffold NestJS sidecar with config, CORS, and dependency setup

.env.example

@@ -0,0 +1,17 @@
+# Server
+PORT=4100
+CORS_ORIGIN=http://localhost:5173
+
+# Fortytwo Platform
+PLATFORM_GRAPHQL_URL=http://localhost:4000/graphql
+PLATFORM_API_KEY=
+
+# Exotel
+EXOTEL_API_KEY=
+EXOTEL_API_TOKEN=
+EXOTEL_ACCOUNT_SID=
+EXOTEL_SUBDOMAIN=api.exotel.com
+EXOTEL_WEBHOOK_SECRET=
+
+# AI
+ANTHROPIC_API_KEY=