feat(index): 指数收敛为固定核心四只 + fuyao 指数快照接入

- 新建 app/services/index_const.py 单一权威: 展示层固定四只核心指数
  (上证/深证成指/创业板/科创综指), quote_service/overview/
  market_overview_builder/sector_monitor 四处重复定义全部收敛
- fuyao 插件接入指数快照端点 (/api/a-share-index/prices/snapshot):
  client 增加 index_snapshot (批量上限 627 码), provider 实现可选协议
  get_realtime_indices — .BJ 后缀先行过滤 (未知代码整批 1002 连坐),
  volume 不做股转手; 修复 fuyao 路由下指数冻结在日K兜底的 bug
- quote_service 自定义源分支鸭子类型调用 get_realtime_indices 补拉指数,
  请求清单 = 核心四只 + 启用指数监控规则标的; 未实现的源走日K兜底
- TickFlow 分支指数固定按码显式拉取, 移除 CN_Index 全量 universe 与
  mode core/all 分支; 指数落盘固定 merge 不截断
- 指数偏好全套下线: realtime_index_symbols / sidebar_index_symbols /
  indices_nav_pinned / realtime_pull_index / realtime_index_mode
- /api/index/list 与 /search (全指数浏览搜索) 删除; daily/minute 保留
  供指数详情页, sync_instruments/sync_daily 保留供数据页
- sector_monitor 指数标的恒可监控, catalog 签名不再依赖指数偏好
- 新增 7 个用例: 指数快照映射/.BJ 过滤/软失败 + 自定义源指数补充链路
  (含监控规则并入/无协议源静默/指数失败软降级)

backend/app/api/settings.py

@@ -489,7 +489,6 @@ def get_preferences() -> dict:
     return {
         "realtime_quotes_enabled": preferences.get_realtime_quotes_enabled(),
         "realtime_allowed": _realtime_allowed(),
-        "indices_nav_pinned": preferences.get_indices_nav_pinned(),
         "watchlist_groups_in_nav": preferences.get_watchlist_groups_in_nav(),
         "minute_sync_enabled": preferences.get_minute_sync_enabled(),
         "minute_sync_days": preferences.get_minute_sync_days(),
@@ -531,7 +530,6 @@ def get_preferences() -> dict:
         "wecom_bot_enabled": preferences.get_wecom_bot_enabled(),
         "webhook_enabled_default": preferences.get_webhook_enabled_default(),
         "webhook_default_channels": preferences.get_webhook_default_channels(),
-        "sidebar_index_symbols": preferences.get_sidebar_index_symbols(),
         "minute_intraday_refresh": preferences.get_minute_intraday_refresh(),
         "minute_intraday_refresh_interval": preferences.get_minute_intraday_refresh_interval(),
         "monitor_ext_fields": preferences.get_monitor_ext_fields(),
@@ -901,9 +899,6 @@ class RealtimeQuotesPrefs(BaseModel):
 class RealtimeQuoteScopePrefs(BaseModel):
     realtime_pull_stock: bool | None = None
     realtime_pull_etf: bool | None = None
-    realtime_pull_index: bool | None = None
-    realtime_index_mode: str | None = None
-    realtime_index_symbols: list[str] | None = None
 
 
 @router.put("/preferences/realtime-quotes")
@@ -985,19 +980,6 @@ def update_realtime_quote_scope(req: RealtimeQuoteScopePrefs) -> dict:
     return preferences.set_realtime_quote_scope(cfg)
 
 
-class IndicesNavPinnedPrefs(BaseModel):
-    indices_nav_pinned: bool
-
-
-@router.put("/preferences/indices-nav-pinned")
-def update_indices_nav_pinned(req: IndicesNavPinnedPrefs) -> dict:
-    """保存侧栏指数报价卡片固定显示开关。
-    ON=常驻显示；OFF=跟随实时行情开关（仅实时开时显示）。"""
-    from app.services import preferences
-    preferences.save({"indices_nav_pinned": req.indices_nav_pinned})
-    return {"indices_nav_pinned": req.indices_nav_pinned}
-
-
 class WatchlistGroupsInNavPrefs(BaseModel):
     watchlist_groups_in_nav: bool
 
@@ -1014,7 +996,6 @@ class RealtimeMonitorConfigIn(BaseModel):
     sse_refresh_pages: dict[str, bool] | None = None
     strategy_monitor_enabled: bool | None = None
     strategy_monitor_ids: list[str] | None = None
-    sidebar_index_symbols: list[str] | None = None
     screener_auto_run: bool | None = None
     minute_intraday_refresh: bool | None = None
     minute_intraday_refresh_interval: int | None = None