Add Docker support for Gateway and SDK documentation

- Add Dockerfile and build script for Gateway containerization
- Add USAGE.md documenting SDK usage for Client/Agent implementations
- Move socket.io-client to production dependencies (required by SDK)
- Remove redundant timestamp field from RoutedMessage (UUID v7 contains timestamp)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/gateway/scripts/build-and-push.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+GATEWAY_DIR="$(dirname "$SCRIPT_DIR")"
+PROJECT_ROOT="$(cd "$GATEWAY_DIR/../.." && pwd)"
+
+REPO="085931705009.dkr.ecr.us-west-2.amazonaws.com/super-multica/gateway"
+BRANCH="$(git symbolic-ref --short -q HEAD | tr '/' '-')"
+IMAGE_TAG="$(date +%F_%H-%M-%S)-${BRANCH}-$(git rev-parse --short HEAD)"
+IMAGE="$REPO:$IMAGE_TAG"
+
+# Determine if sudo is needed for docker commands
+if [[ "$(uname -s)" == "Linux" ]]; then
+    DOCKER_CMD="sudo docker"
+else
+    DOCKER_CMD="docker"
+fi
+
+echo "Building image: $IMAGE"
+echo "Using Dockerfile: $GATEWAY_DIR/Dockerfile"
+echo "Build context: $PROJECT_ROOT"
+
+# Login to ECR
+aws ecr get-login-password --region us-west-2 | $DOCKER_CMD login --username AWS --password-stdin 085931705009.dkr.ecr.us-west-2.amazonaws.com
+
+# Build from project root with gateway Dockerfile
+$DOCKER_CMD build -f "$GATEWAY_DIR/Dockerfile" -t "$IMAGE" "$PROJECT_ROOT"
+$DOCKER_CMD push "$IMAGE"
+
+echo ""
+echo "Successfully pushed: $IMAGE"