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

lib/processingScheduler.ts

@@ -254,7 +254,9 @@ async function processQuestions(
   });
 
   // Filter and prepare unique questions
-  const uniqueQuestions = Array.from(new Set(questions.filter((q) => q.trim())));
+  const uniqueQuestions = Array.from(
+    new Set(questions.filter((q) => q.trim()))
+  );
   if (uniqueQuestions.length === 0) return;
 
   // Batch create questions (skip duplicates)