test: add integration test suite + canary deployment script

Integration tests:
- internal/serviceadapter/integration_test.go (8 test cases)
- Tests real gateway: health, routing, 404s, auth flow
- Configurable via GATEWAY_URL, TEST_JWT_TOKEN, SKIP_AUTH_TESTS

Canary deployment script:
- scripts/test-canary.sh: scale→1, test, scale→N on pass
- Keeps 1 pod for debugging on test failure
- Supports custom NAMESPACE, DEPLOYMENT, REPLICAS

Usage:
- Local: ./scripts/test-integration.sh
- Production: GATEWAY_URL=https://api.riotpiao.com ./scripts/test-integration.sh
- Canary: ./scripts/test-canary.sh

Added INTEGRATION_TESTS.md with full documentation.

scripts/test-integration.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+# Run integration tests against real gateway
+# Usage:
+#   ./scripts/test-integration.sh                           # Test local gateway
+#   GATEWAY_URL=https://api.riotpiao.com ./scripts/test-integration.sh  # Test production
+
+set -e
+
+GATEWAY_URL=${GATEWAY_URL:-http://localhost:8080}
+SKIP_AUTH_TESTS=${SKIP_AUTH_TESTS:-true}
+TEST_TIMEOUT=${TEST_TIMEOUT:-10}
+
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+echo "Integration Tests"
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+echo "Gateway URL:     $GATEWAY_URL"
+echo "Skip Auth Tests: $SKIP_AUTH_TESTS"
+echo "Timeout:         ${TEST_TIMEOUT}s"
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+
+export GATEWAY_URL
+export SKIP_AUTH_TESTS
+export TEST_TIMEOUT
+
+go test -tags integration -v ./internal/serviceadapter -run TestIntegration