feat: add comprehensive performance benchmark tracking system

- Create benchmark test suites for critical operations:
  - Node loading performance
  - Database query performance
  - Search operations performance
  - Validation performance
  - MCP tool execution performance

- Add GitHub Actions workflow for benchmark tracking:
  - Runs on push to main and PRs
  - Uses github-action-benchmark for historical tracking
  - Comments on PRs with performance results
  - Alerts on >10% performance regressions
  - Stores results in GitHub Pages

- Create benchmark infrastructure:
  - Custom Vitest benchmark configuration
  - JSON reporter for CI results
  - Result formatter for github-action-benchmark
  - Performance threshold documentation

- Add supporting utilities:
  - SQLiteStorageService for benchmark database setup
  - MCPEngine wrapper for testing MCP tools
  - Test factories for generating benchmark data
  - Enhanced NodeRepository with benchmark methods

- Document benchmark system:
  - Comprehensive benchmark guide in docs/BENCHMARKS.md
  - Performance thresholds in .github/BENCHMARK_THRESHOLDS.md
  - README for benchmarks directory
  - Integration with existing test suite

The benchmark system will help monitor performance over time and catch regressions before they reach production.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.env.test

@@ -0,0 +1,127 @@
+# Test Environment Configuration for n8n-mcp
+# This file contains test-specific environment variables
+# DO NOT commit sensitive values - use .env.test.local for secrets
+
+# === Test Mode Configuration ===
+NODE_ENV=test
+MCP_MODE=test
+TEST_ENVIRONMENT=true
+
+# === Database Configuration ===
+# Use in-memory database for tests by default
+NODE_DB_PATH=:memory:
+# Uncomment to use a persistent test database
+# NODE_DB_PATH=./tests/fixtures/test-nodes.db
+REBUILD_ON_START=false
+
+# === API Configuration for Mocking ===
+# Mock API endpoints
+N8N_API_URL=http://localhost:3001/mock-api
+N8N_API_KEY=test-api-key-12345
+N8N_WEBHOOK_BASE_URL=http://localhost:3001/webhook
+N8N_WEBHOOK_TEST_URL=http://localhost:3001/webhook-test
+
+# === Test Server Configuration ===
+PORT=3001
+HOST=127.0.0.1
+CORS_ORIGIN=http://localhost:3000,http://localhost:5678
+
+# === Authentication ===
+AUTH_TOKEN=test-auth-token
+MCP_AUTH_TOKEN=test-mcp-auth-token
+
+# === Logging Configuration ===
+# Set to 'debug' for verbose test output
+LOG_LEVEL=error
+# Enable debug logging for specific tests
+DEBUG=false
+# Log test execution details
+TEST_LOG_VERBOSE=false
+
+# === Test Execution Configuration ===
+# Test timeouts (in milliseconds)
+TEST_TIMEOUT_UNIT=5000
+TEST_TIMEOUT_INTEGRATION=15000
+TEST_TIMEOUT_E2E=30000
+TEST_TIMEOUT_GLOBAL=60000
+
+# Test retry configuration
+TEST_RETRY_ATTEMPTS=2
+TEST_RETRY_DELAY=1000
+
+# Parallel execution
+TEST_PARALLEL=true
+TEST_MAX_WORKERS=4
+
+# === Feature Flags ===
+# Enable/disable specific test features
+FEATURE_TEST_COVERAGE=true
+FEATURE_TEST_SCREENSHOTS=false
+FEATURE_TEST_VIDEOS=false
+FEATURE_TEST_TRACE=false
+FEATURE_MOCK_EXTERNAL_APIS=true
+FEATURE_USE_TEST_CONTAINERS=false
+
+# === Mock Service Configuration ===
+# MSW (Mock Service Worker) configuration
+MSW_ENABLED=true
+MSW_API_DELAY=0
+
+# Test data paths
+TEST_FIXTURES_PATH=./tests/fixtures
+TEST_DATA_PATH=./tests/data
+TEST_SNAPSHOTS_PATH=./tests/__snapshots__
+
+# === Performance Testing ===
+# Performance thresholds (in milliseconds)
+PERF_THRESHOLD_API_RESPONSE=100
+PERF_THRESHOLD_DB_QUERY=50
+PERF_THRESHOLD_NODE_PARSE=200
+
+# === External Service Mocks ===
+# Redis mock (if needed)
+REDIS_MOCK_ENABLED=true
+REDIS_MOCK_PORT=6380
+
+# Elasticsearch mock (if needed)
+ELASTICSEARCH_MOCK_ENABLED=false
+ELASTICSEARCH_MOCK_PORT=9201
+
+# === Rate Limiting ===
+# Disable rate limiting in tests
+RATE_LIMIT_MAX=0
+RATE_LIMIT_WINDOW=0
+
+# === Cache Configuration ===
+# Disable caching in tests for predictable results
+CACHE_TTL=0
+CACHE_ENABLED=false
+
+# === Error Handling ===
+# Show full error stack traces in tests
+ERROR_SHOW_STACK=true
+ERROR_SHOW_DETAILS=true
+
+# === Cleanup Configuration ===
+# Automatically clean up test data after each test
+TEST_CLEANUP_ENABLED=true
+TEST_CLEANUP_ON_FAILURE=false
+
+# === Database Seeding ===
+# Seed test database with sample data
+TEST_SEED_DATABASE=true
+TEST_SEED_TEMPLATES=true
+
+# === Network Configuration ===
+# Network timeouts for external requests
+NETWORK_TIMEOUT=5000
+NETWORK_RETRY_COUNT=0
+
+# === Memory Limits ===
+# Set memory limits for tests (in MB)
+TEST_MEMORY_LIMIT=512
+
+# === Code Coverage ===
+# Coverage output directory
+COVERAGE_DIR=./coverage
+COVERAGE_REPORTER=lcov,html,text-summary