feat: add integration tests and hadolint to CI pipeline

tests/test.sh

@@ -0,0 +1,72 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+IMAGE="${1:?Usage: test.sh <image>}"
+CONTAINER_NAME="test-$(basename "$IMAGE")-$$"
+PASSED=0
+FAILED=0
+TOTAL=0
+
+cleanup() {
+  docker rm -f "$CONTAINER_NAME" >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
+assert() {
+  local name="$1" expected="$2" actual="$3"
+  TOTAL=$((TOTAL + 1))
+  if [ "$expected" = "$actual" ]; then
+    echo "  PASS: $name"
+    PASSED=$((PASSED + 1))
+  else
+    echo "  FAIL: $name (expected: '$expected', got: '$actual')"
+    FAILED=$((FAILED + 1))
+  fi
+}
+
+assert_match() {
+  local name="$1" pattern="$2" actual="$3"
+  TOTAL=$((TOTAL + 1))
+  if echo "$actual" | grep -qE "$pattern"; then
+    echo "  PASS: $name"
+    PASSED=$((PASSED + 1))
+  else
+    echo "  FAIL: $name (pattern: '$pattern', got: '$actual')"
+    FAILED=$((FAILED + 1))
+  fi
+}
+
+echo "Running container: $IMAGE"
+docker run -d --name "$CONTAINER_NAME" -p 0:8080 "$IMAGE" >/dev/null
+
+HOST_PORT=$(docker port "$CONTAINER_NAME" 8080/tcp | head -1 | cut -d: -f2)
+BASE_URL="http://127.0.0.1:${HOST_PORT}"
+
+echo "Waiting for container (port $HOST_PORT)..."
+for i in $(seq 1 30); do
+  if curl -sf "$BASE_URL/" >/dev/null 2>&1; then
+    echo "Container ready after ${i}s"
+    break
+  fi
+  if [ "$i" -eq 30 ]; then
+    echo "FAIL: Container did not become ready within 30s"
+    docker logs "$CONTAINER_NAME"
+    exit 1
+  fi
+  sleep 1
+done
+
+echo ""
+echo "Test: GET /"
+RESPONSE=$(curl -sf -D - "$BASE_URL/")
+STATUS=$(echo "$RESPONSE" | head -1 | grep -oP '\d{3}')
+CONTENT_TYPE=$(echo "$RESPONSE" | grep -i 'content-type' | tr -d '\r' | cut -d: -f2- | xargs)
+BODY=$(echo "$RESPONSE" | tail -1)
+
+assert "HTTP status is 200" "200" "$STATUS"
+assert_match "Content-Type is application/json" "application/json" "$CONTENT_TYPE"
+assert_match "Body contains valid IP" '^(\"[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+\"|\"[0-9a-fA-F:]+\")$' "$BODY"
+
+echo ""
+echo "Results: $PASSED/$TOTAL passed, $FAILED failed"
+[ "$FAILED" -eq 0 ]