Fix project detail 500 error and round deletion data integrity

- Add missing migration for FileRequirement table and ProjectFile.requirementId
  column (existed in Prisma schema but had no migration, causing all queries
  with `include: { files: true }` to fail with column not found)
- Make projectTags query resilient with try-catch in project.get
- Reset project status to SUBMITTED when round is deleted (prevents orphaned
  ASSIGNED status after ON DELETE SET NULL nullifies roundId)
- Fix round creation/update to allow requiredReviews=0 for filtering rounds
- Parse Zod validation errors in round creation error display

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

src/app/(admin)/admin/rounds/new/page.tsx

@@ -417,7 +417,20 @@ function CreateRoundContent() {
               <CardContent className="flex items-center gap-2 py-4">
                 <AlertCircle className="h-5 w-5 text-destructive" />
                 <p className="text-sm text-destructive">
-                  {createRound.error.message}
+                  {(() => {
+                    const msg = createRound.error.message
+                    try {
+                      const parsed = JSON.parse(msg)
+                      if (Array.isArray(parsed)) {
+                        return parsed.map((e: { message?: string; path?: string[] }) =>
+                          e.message || 'Validation error'
+                        ).join('. ')
+                      }
+                    } catch {
+                      // Not JSON, use as-is
+                    }
+                    return msg
+                  })()}
                 </p>
               </CardContent>
             </Card>