feat(phase-6): Bulk CSV processing and background worker implementation

- Add BulkJob model to Prisma schema with relations
- Implement BulkProcessorService for CSV parsing and job management
- Create BulkTrackingWorker for background processing with BullMQ
- Add comprehensive bulk API routes (upload, jobs, progress, export)
- Integrate multer for CSV file uploads with validation
- Add job progress tracking and estimation
- Implement CSV export functionality for results
- Add queue statistics and cleanup endpoints
- Create shared types for bulk processing
- Add comprehensive test suite for all bulk functionality
- Implement graceful worker shutdown and error handling
- Add rate limiting and authentication for all bulk endpoints

Backward compatibility: Maintained for /api/track and /api/v1/track

packages/database/prisma/schema.prisma

@@ -22,6 +22,7 @@ model User {
   
   memberships   OrgMembership[]
   auditLogs     AuditLog[]
+  bulkJobs      BulkJob[]
   
   @@map("users")
 }
@@ -36,6 +37,7 @@ model Organization {
   projects    Project[]
   apiKeys     ApiKey[]
   auditLogs   AuditLog[]
+  bulkJobs    BulkJob[]
   
   @@map("organizations")
 }
@@ -212,6 +214,32 @@ model AuditLog {
   @@map("audit_logs")
 }
 
+model BulkJob {
+  id             String    @id
+  userId         String
+  organizationId String?
+  projectId      String?
+  status         String    // 'pending' | 'processing' | 'completed' | 'failed' | 'cancelled'
+  totalUrls      Int
+  processedUrls  Int       @default(0)
+  successfulUrls Int       @default(0)
+  failedUrls     Int       @default(0)
+  configJson     Json      // Job configuration (options)
+  urlsJson       Json      // Array of URLs to process
+  resultsJson    Json?     // Array of results
+  createdAt      DateTime  @default(now())
+  startedAt      DateTime?
+  finishedAt     DateTime?
+  
+  user         User          @relation(fields: [userId], references: [id], onDelete: Cascade)
+  organization Organization? @relation(fields: [organizationId], references: [id], onDelete: SetNull)
+  project      Project?      @relation(fields: [projectId], references: [id], onDelete: SetNull)
+  
+  @@index([userId, createdAt])
+  @@index([status, createdAt])
+  @@map("bulk_jobs")
+}
+
 enum Role {
   OWNER
   ADMIN