Add visual progress indicator for AI assignment batches

- Add AssignmentJob model to track AI assignment progress
- Create startAIAssignmentJob mutation for background processing
- Add getAIAssignmentJobStatus query for polling progress
- Update AI assignment service with progress callback support
- Add progress bar UI showing batch/project processing status
- Add toast notifications for job completion/failure
- Add AI_SUGGESTIONS_READY notification type

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

prisma/schema.prisma

@@ -374,6 +374,7 @@ model Round {
   filteringRules    FilteringRule[]
   filteringResults  FilteringResult[]
   filteringJobs     FilteringJob[]
+  assignmentJobs    AssignmentJob[]
 
   @@index([programId])
   @@index([status])
@@ -1092,6 +1093,38 @@ enum FilteringJobStatus {
   FAILED
 }
 
+// Tracks progress of long-running AI assignment jobs
+model AssignmentJob {
+  id               String            @id @default(cuid())
+  roundId          String
+  status           AssignmentJobStatus @default(PENDING)
+  totalProjects    Int               @default(0)
+  totalBatches     Int               @default(0)
+  currentBatch     Int               @default(0)
+  processedCount   Int               @default(0)
+  suggestionsCount Int               @default(0)
+  errorMessage     String?           @db.Text
+  startedAt        DateTime?
+  completedAt      DateTime?
+  fallbackUsed     Boolean           @default(false)
+
+  createdAt        DateTime          @default(now())
+  updatedAt        DateTime          @updatedAt
+
+  // Relations
+  round Round @relation(fields: [roundId], references: [id], onDelete: Cascade)
+
+  @@index([roundId])
+  @@index([status])
+}
+
+enum AssignmentJobStatus {
+  PENDING
+  RUNNING
+  COMPLETED
+  FAILED
+}
+
 // =============================================================================
 // SPECIAL AWARDS SYSTEM
 // =============================================================================