AI-powered assignment generation with enriched data and streaming UI

- Add aiPreview mutation with full project/juror data (bios, descriptions,
  documents, categories, ocean issues, countries, team sizes)
- Increase AI description limit from 300 to 2000 chars for richer context
- Update GPT system prompt to use all available data fields
- Add mode toggle (AI default / Algorithm fallback) in assignment preview
- Lift AI mutation to parent page for background generation persistence
- Show visual indicator on page while AI generates (spinner + progress card)
- Toast notification with "Review" action when AI completes
- Staggered reveal animation for assignment results (streaming feel)
- Fix assignment balance with dynamic penalty (25pts per existing assignment)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/(admin)/admin/competitions/[competitionId]/assignments/page.tsx

@@ -2,7 +2,8 @@
 
 import { useState } from 'react'
 import { useParams, useRouter } from 'next/navigation'
-import { ArrowLeft, PlayCircle } from 'lucide-react'
+import { ArrowLeft, Loader2, PlayCircle, Zap } from 'lucide-react'
+import { toast } from 'sonner'
 import { trpc } from '@/lib/trpc/client'
 import { Button } from '@/components/ui/button'
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
@@ -26,6 +27,16 @@ export default function AssignmentsDashboardPage() {
   const [selectedRoundId, setSelectedRoundId] = useState<string>('')
   const [previewSheetOpen, setPreviewSheetOpen] = useState(false)
 
+  const aiAssignmentMutation = trpc.roundAssignment.aiPreview.useMutation({
+    onSuccess: () => {
+      toast.success('AI assignments ready!', {
+        action: { label: 'Review', onClick: () => setPreviewSheetOpen(true) },
+        duration: 10000,
+      })
+    },
+    onError: (err) => toast.error(`AI generation failed: ${err.message}`),
+  })
+
   const { data: competition, isLoading: isLoadingCompetition } = trpc.competition.getById.useQuery({
     id: competitionId,
   })
@@ -104,11 +115,24 @@ export default function AssignmentsDashboardPage() {
 
       {selectedRoundId && (
         <div className="space-y-6">
-          <div className="flex justify-end">
-            <Button onClick={() => setPreviewSheetOpen(true)}>
-              <PlayCircle className="mr-2 h-4 w-4" />
-              Generate Assignments
+          <div className="flex justify-end gap-2">
+            <Button
+              onClick={() => {
+                aiAssignmentMutation.mutate({ roundId: selectedRoundId, requiredReviews })
+              }}
+              disabled={aiAssignmentMutation.isPending}
+            >
+              {aiAssignmentMutation.isPending ? (
+                <><Loader2 className="mr-2 h-4 w-4 animate-spin" />Generating...</>
+              ) : (
+                <><Zap className="mr-2 h-4 w-4" />{aiAssignmentMutation.data ? 'Regenerate' : 'Generate with AI'}</>
+              )}
             </Button>
+            {aiAssignmentMutation.data && (
+              <Button variant="outline" onClick={() => setPreviewSheetOpen(true)}>
+                Review Assignments
+              </Button>
+            )}
           </div>
 
           <Tabs defaultValue="coverage" className="w-full">
@@ -170,6 +194,10 @@ export default function AssignmentsDashboardPage() {
             open={previewSheetOpen}
             onOpenChange={setPreviewSheetOpen}
             requiredReviews={requiredReviews}
+            aiResult={aiAssignmentMutation.data ?? null}
+            isAIGenerating={aiAssignmentMutation.isPending}
+            onGenerateAI={() => aiAssignmentMutation.mutate({ roundId: selectedRoundId, requiredReviews })}
+            onResetAI={() => aiAssignmentMutation.reset()}
           />
         </div>
       )}