feat(ncm §20): 音质体系全量——八档UI/VIP检测缓存/逐级降级下首恢复/fee门禁/默认极高HQ

- core: 9档枚举(顺序=降级链, DOLBY映射保留不进UI/链) + level_key(sky/sky_c51)
  + level_gate(CVIP/SVIP门槛) + song_url surround档附加immerseType=c51
  + song_url_auto全档表降级(out_level回填/响应level静默降档采信/try_fn可注入)
  + vip_info(weapi v2优先v1兜底) + parse_vip_info离线可测 + NCM_ERR_VIP(-15)
- app/logic/account.c(新): account.json会员态缓存(uid/nick/vip/双expire/checked_at)
  刷新=登录后/超1天/到期后各一次不轮询; account_vip本地到期降档视图
- player_manager: 用户档按会员钳顶后逐级降级(不硬拒,缓存键仍用户档),
  fee∈{1,4}且非会员→NCM_ERR_VIP零请求(缓存命中优先), eff_level回填
- UI: 设置页八档(规格+门槛+未解锁标注,允许选定), 播放页时间行中央
  生效档/已降级至xx小字, VIP专享文案; 默认档Hi-Res→极高HQ(存量设置保留)
- 验证(0真实请求): degrade_sim 90例矩阵全PASS; player_flow_sim P1-P8全PASS;
  test_ncm_core vip解析9例宿主+qemu全PASS; 窗口/分页/缓存/封面/audiod sim全PASS;
  mipsel -Wall -Wextra 0 warning; 6页离屏rc=0。未部署真机(留主会话)

.gitignore

@@ -91,3 +91,4 @@ patch_v2/ncm_app/audiod_chain_sim
 patch_v2/ncm_app/window_sim
 patch_v2/ncm_app/cover_chain_sim
 patch_v2/ncm_app/player_flow_sim
+patch_v2/ncm_app/degrade_sim