feat: add useBalancedRanking flag to round config schema

Defaults to true so existing rounds preserve current behavior; toggled
per-round from the ranking dashboard side panel.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/types/competition-configs.ts

@@ -142,6 +142,11 @@ export const EvaluationConfigSchema = z.object({
     })
     .optional(),
 
+  // Whether the ranking dashboard ranks projects by juror-balanced (z-normalized)
+  // average. Defaulting to true preserves existing behavior. Toggled per-round
+  // from the dashboard side panel.
+  useBalancedRanking: z.boolean().default(true),
+
   // Ranking (Phase 1)
   rankingEnabled: z.boolean().default(false),
   rankingCriteria: z.string().optional(),