fix: show affinity badge for enabled accounts even with 0 clients

- Backend: remove count > 0 filter in GetAccountAffinityCountBatch so
  accounts with 0 bound clients are included in the response
- Frontend: change badge condition from affinityClientCount > 0 to
  account.client_affinity_enabled so the badge always shows for accounts
  with affinity enabled

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

backend/internal/repository/gateway_cache.go

@@ -188,9 +188,7 @@ func (c *gatewayCache) GetAccountAffinityCountBatch(ctx context.Context, account
 		if err != nil && err != redis.Nil {
 			continue
 		}
-		if count > 0 {
-			result[id] = count
-		}
+		result[id] = count
 	}
 	return result, nil
 }

frontend/src/components/account/AccountStatusIndicator.vue

@@ -2,7 +2,7 @@
   <div class="flex items-center gap-2">
     <!-- Affinity Client Count Badge -->
     <div
-      v-if="affinityClientCount > 0"
+      v-if="account.client_affinity_enabled"
       class="group/affinity relative"
       @mouseenter="loadAffinityClients"
     >