fix: fetch_market.py change_pct 输出纯数值，方向符号由前端渲染

- change_pct 从 "▲ 2.26%" 改为 "2.26%"，is_up 控制方向
- 与 brief.html 前端渲染逻辑对齐，避免重复方向符号
- 修复 A 股超时后 cn_indices 为空导致行情行缺失的问题

scripts/fetch_market.py

@@ -23,13 +23,12 @@ def fetch_crypto():
                 continue
             price = data[coin_id]["usd"]
             change = data[coin_id].get("usd_24h_change", 0) or 0
-            direction = "▲" if change >= 0 else "▼"
             items.append({
                 "type": "crypto",
                 "symbol": names[coin_id],
                 "icon": icon,
                 "price": f"${price:,.2f}",
-                "change_pct": f"{direction} {abs(change):.2f}%",
+                "change_pct": f"{abs(change):.2f}%",
                 "is_up": change >= 0,
             })
         return items
@@ -49,13 +48,11 @@ def fetch_cn_indices():
             price = diff.get("f2", 0)
             change = diff.get("f4", 0)
             pct = diff.get("f3", 0)
-            direction = "▲" if change >= 0 else "▼"
             items.append({
                 "type": "cn_index",
                 "symbol": name,
                 "price": f"{price:.2f}",
-                "change": f"{direction} {abs(change):.2f}",
-                "change_pct": f"{direction} {abs(pct):.2f}%",
+                "change_pct": f"{abs(pct):.2f}%",
                 "is_up": change >= 0,
             })
         return items