perf(store): 消除同步复制下的鉴权与心跳锁阻塞

将 Worker 心跳与容量分配事务设为本地异步提交，避免同步副本延迟期间长期持有全局分配锁。API Key 使用时间改为异步提交并按分钟合并，消除高并发请求对同一热行的锁排队。业务任务、钱包、结算、并发租约等关键数据仍保持同步复制。验证通过完整 Go 测试、go vet、竞态测试、迁移安全检查及 PostgreSQL 18 集成测试。

apps/api/internal/store/postgres.go

@@ -1709,7 +1709,19 @@ WHERE k.key_prefix = $1
 		if bcrypt.CompareHashAndPassword([]byte(candidate.hash), []byte(secret)) != nil {
 			continue
 		}
-		if _, err := database.Exec(ctx, `UPDATE gateway_api_keys SET last_used_at = now(), updated_at = now() WHERE id = $1::uuid`, candidate.apiKeyID); err != nil {
+		// API key usage timestamps are telemetry, not authentication state. Keep
+		// their writes off the synchronous-replication critical path and coalesce
+		// hot-key updates so concurrent requests do not contend on the same row.
+		if _, err := database.Exec(ctx, `
+WITH commit_policy AS (
+  SELECT set_config('synchronous_commit', 'off', true)
+)
+UPDATE gateway_api_keys
+SET last_used_at = now(),
+    updated_at = now()
+FROM commit_policy
+WHERE id = $1::uuid
+  AND (last_used_at IS NULL OR last_used_at < now() - interval '1 minute')`, candidate.apiKeyID); err != nil {
 			return nil, err
 		}
 		return &auth.User{