fix: batch 4 — connection pooling, graceful shutdown, email verification UX

- Prisma: connection_limit=10, pool_timeout=30 on DATABASE_URL in both compose files
- Graceful shutdown: SIGTERM/SIGINT forwarded to Node process in docker-entrypoint.sh
- testEmailConnection: replaced real email send with transporter.verify(), simplified UI to single button
- NotificationLog.userId index: confirmed already present, no change needed

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

docker/docker-entrypoint.sh

@@ -59,4 +59,18 @@ else
 fi
 
 echo "==> Starting application..."
-exec node server.js
+
+# Graceful shutdown: forward SIGTERM/SIGINT to the Node process
+# so in-flight requests can complete before the container exits.
+shutdown() {
+  echo "==> Received shutdown signal, stopping gracefully..."
+  kill -TERM "$NODE_PID" 2>/dev/null
+  wait "$NODE_PID"
+  exit $?
+}
+
+trap shutdown TERM INT
+
+node server.js &
+NODE_PID=$!
+wait "$NODE_PID"