feat(infra): auto-create n8n Postgres credential from .env

Postgres credential only needs simple connection params (host, port,
db, user, password) — safe to automate via CLI import.
Google Sheets credential still requires manual UI setup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ImTotem

infra/scripts/init_n8n.sh

@@ -1,9 +1,9 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-# n8n workflow import + owner setup
+# n8n workflow import + owner setup + Postgres credential
 # Idempotent: skips if already configured
-# Credentials (Postgres, Google Sheets) must be set up manually in n8n UI
+# Google Sheets credential must be set up manually in n8n UI
 
 COMPOSE="sudo docker compose -p bcsd-app --env-file .env -f infra/docker/docker-compose.yml"
 MAX_RETRIES=15
@@ -65,6 +65,36 @@ print('setup' if d.get('userManagement',{}).get('showSetupOnFirstLoad') else 'do
     echo "  Owner created: ${N8N_AUTH_USER}@bcsdlab.com"
 }
 
+setup_pg_credential() {
+    local existing
+    existing=$($COMPOSE exec -T n8n n8n list:credential 2>&1 | grep -c "BCSD PostgreSQL" || true)
+    if [ "$existing" -gt 0 ]; then
+        echo "  Postgres credential already exists — skipping"
+        return 0
+    fi
+    echo "  Creating Postgres credential from .env..."
+    set -a; source .env; set +a
+    local cred_json
+    cred_json=$(python3 -c "
+import json, sys, uuid
+cred = [{
+    'id': str(uuid.uuid4()),
+    'name': 'BCSD PostgreSQL',
+    'type': 'postgres',
+    'data': {
+        'host': '${POSTGRES_HOST:-postgres}',
+        'port': ${POSTGRES_PORT:-5432},
+        'database': '${POSTGRES_DB}',
+        'user': '${POSTGRES_USER}',
+        'password': '${POSTGRES_PASSWORD}',
+        'ssl': 'disable'
+    }
+}]
+json.dump(cred, sys.stdout)
+")
+    echo "$cred_json" | $COMPOSE exec -T n8n n8n import:credentials --input=/dev/stdin
+}
+
 echo "=== n8n Init ==="
 
 echo "1. Starting n8n..."
@@ -80,9 +110,12 @@ fi
 echo "3. Setting up owner account..."
 setup_owner
 
-echo "4. Importing workflows..."
+echo "4. Setting up Postgres credential..."
+setup_pg_credential
+
+echo "5. Importing workflows..."
 import_workflow "/workflows/pg_sheets_sync.json" "PG → Sheets Sync (5min)"
 import_workflow "/workflows/link_auto_expire.json" "Link Auto-Expiration (hourly)"
 
 echo "=== n8n Init complete ==="
-echo "NOTE: Set up Postgres + Google Sheets credentials in n8n UI if first deploy"
+echo "NOTE: Set up Google Sheets credential in n8n UI if first deploy"