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/importProcessor.ts

@@ -434,7 +434,7 @@ async function processQueuedImportsInternal(batchSize = 50): Promise<void> {
     // Process with concurrency limit to avoid overwhelming the database
     const concurrencyLimit = 5;
     const results: Array<{
-      importRecord: typeof unprocessedImports[0];
+      importRecord: (typeof unprocessedImports)[0];
       result: Awaited<ReturnType<typeof processSingleImport>>;
     }> = [];