feat: implement comprehensive email system with rate limiting and extensive test suite

- Add robust email service with rate limiting and configuration management
- Implement shared rate limiter utility for consistent API protection
- Create comprehensive test suite for core processing pipeline
- Add API tests for dashboard metrics and authentication routes
- Fix date range picker infinite loop issue
- Improve session lookup in refresh sessions API
- Refactor session API routing with better code organization
- Update processing pipeline status monitoring
- Clean up leftover files and improve code formatting

package.json

@@ -95,6 +95,7 @@
   "devDependencies": {
     "@eslint/eslintrc": "^3.3.1",
     "@eslint/js": "^9.30.0",
+    "@next/eslint-plugin-next": "^15.3.4",
     "@playwright/test": "^1.53.1",
     "@tailwindcss/postcss": "^4.1.11",
     "@testing-library/dom": "^10.4.0",