fix(HEL-487): 盘中当天看板在 rt_k 无权限时降级到免费实时源

rt_k 失败、无权限、超时或空结果时改用东财全市场快照，再失败则用腾讯批量行情；两者都失败仍不退回昨天。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

backend/data/providers/tushare_indices.py

@@ -59,6 +59,12 @@ class IndexMixin:
         }
 
     def realtime_market_indices(self, requested_date: str) -> dict[str, Any]:
+        try:
+            return self._tushare_realtime_market_indices(requested_date)
+        except TushareError:
+            return self._free_realtime_market_indices(requested_date)
+
+    def _tushare_realtime_market_indices(self, requested_date: str) -> dict[str, Any]:
         trade_date, _ = self.resolve_trade_context(requested_date)
         index_names = {
             "000001.SH": "上证指数",
@@ -116,3 +122,52 @@ class IndexMixin:
                 "average_return_20d": 0,
             },
         }
+
+    def _free_realtime_market_indices(self, requested_date: str) -> dict[str, Any]:
+        trade_date, _ = self.resolve_trade_context(requested_date)
+        aggregator = getattr(self, "realtime_aggregator", None)
+        if aggregator is None:
+            raise TushareError("免费实时源未配置")
+        quotes = aggregator.eastmoney_indices()
+        index_names = {
+            "000001": ("000001.SH", "上证指数"),
+            "399001": ("399001.SZ", "深证成指"),
+            "399006": ("399006.SZ", "创业板指"),
+        }
+        indices = []
+        for quote in quotes:
+            mapped = index_names.get(str(quote.get("code") or ""))
+            if not mapped:
+                continue
+            ts_code, name = mapped
+            close = _number(quote.get("price"))
+            previous_close = _number(quote.get("previous_close"))
+            if close <= 0 or previous_close <= 0:
+                continue
+            indices.append(
+                {
+                    "ts_code": ts_code,
+                    "name": str(quote.get("name") or name).strip(),
+                    "trade_date": trade_date,
+                    "close": close,
+                    "pct_chg": round(_number(quote.get("change")) or (close / previous_close - 1) * 100, 3),
+                    "return_5d": 0,
+                    "amount_billion": round(_number(quote.get("amount_billion")), 2),
+                    "quote_time": quote.get("quote_time") or "",
+                    "source": quote.get("source") or "eastmoney_push2",
+                }
+            )
+        if len(indices) != 3:
+            raise TushareError("Realtime index quotes are incomplete")
+        return {
+            "trade_date": trade_date,
+            "source": "eastmoney_push2",
+            "realtime": True,
+            "precise": True,
+            "indices": indices,
+            "aggregate": {
+                "average_pct_chg": round(sum(item["pct_chg"] for item in indices) / len(indices), 3),
+                "average_return_5d": 0,
+                "average_return_20d": 0,
+            },
+        }