feat(logging): add structured logging module with Winston, CloudWatch…

.env.example

@@ -31,9 +31,39 @@ RATE_LIMIT_ENTERPRISE_PER_MINUTE=10000
 RATE_LIMIT_WINDOW_MS=60000
 RATE_LIMIT_BURST_MULTIPLIER=1.2
 
-# Logging
+# ── Logging ────────────────────────────────────────────────────────────────
+# Minimum log level emitted to all transports.
+# Values: verbose | debug | info | warn | error | fatal
 LOG_LEVEL=debug
 
+# Human-readable service identifier included in every structured log record.
+SERVICE_NAME=alian-structure-api
+
+# Optional: write daily-rotating log files to this directory.
+# Leave blank to disable file logging (console-only).
+# LOG_FILE_DIR=/var/log/alian-structure
+
+# ── CloudWatch (optional) ───────────────────────────────────────────────────
+# Set CLOUDWATCH_GROUP_NAME and AWS_REGION to enable AWS CloudWatch shipping.
+# CLOUDWATCH_GROUP_NAME=/alian-structure/api
+# CLOUDWATCH_STREAM_NAME=api-server         # default: <hostname>-<pid>
+# AWS_REGION=us-east-1
+# AWS_ACCESS_KEY_ID=                        # optional; prefer IAM role
+# AWS_SECRET_ACCESS_KEY=                    # optional; prefer IAM role
+# CLOUDWATCH_UPLOAD_RATE_MS=2000            # flush interval (default: 2000ms)
+# CLOUDWATCH_RETENTION_DAYS=30             # log retention (default: 30 days)
+# CLOUDWATCH_LOG_LEVEL=info                # min level shipped to CloudWatch
+
+# ── Elasticsearch / ELK (optional) ─────────────────────────────────────────
+# Set ELASTICSEARCH_URL to enable ELK shipping.
+# ELASTICSEARCH_URL=http://localhost:9200
+# ELASTICSEARCH_INDEX_PREFIX=logs-alian-structure
+# ELASTICSEARCH_USERNAME=
+# ELASTICSEARCH_PASSWORD=
+# ELASTICSEARCH_API_KEY=                   # base64-encoded id:api_key
+# ELASTICSEARCH_CA_CERT=                   # path to CA cert file (for TLS)
+# ELASTICSEARCH_LOG_LEVEL=info             # min level shipped to Elasticsearch
+
 # Sentry Error Tracking
 SENTRY_DSN=
 SENTRY_ENVIRONMENT=development