feat: expand production config and documentation for provider integrations

.env.example

@@ -3,11 +3,35 @@ NODE_ENV=production
 PORT=3000
 STATE_FILE_PATH=/data/state.json
 LOG_LEVEL=info
+APP_BASE_URL=https://xartaudio.example.com
 
 # Webhook secrets
 X_WEBHOOK_SECRET=replace-me
 POLAR_WEBHOOK_SECRET=replace-me
 
+# X API
+X_BEARER_TOKEN=replace-me
+X_BOT_USER_ID=replace-me
+
+# Polar API
+POLAR_ACCESS_TOKEN=replace-me
+POLAR_SERVER=production
+POLAR_PRODUCT_IDS=prod_123
+
+# TTS (OpenAI-compatible)
+TTS_API_KEY=replace-me
+TTS_BASE_URL=
+TTS_MODEL=gpt-4o-mini-tts
+TTS_VOICE=alloy
+
+# S3-compatible object storage
+S3_BUCKET=replace-me
+S3_REGION=us-east-1
+S3_ENDPOINT=
+S3_ACCESS_KEY_ID=replace-me
+S3_SECRET_ACCESS_KEY=replace-me
+S3_SIGNED_URL_TTL_SEC=3600
+
 # Credit policy
 BASE_CREDITS=1
 INCLUDED_CHARS=25000