修复温度曲线三个渲染问题：数据点过少、张力过高、canvas被CSS拉伸

- 小时数据插值为每半小时一点（24→47点）
- 全线 tension 从 0.28-0.32 降至 0.1-0.12
- 移除 canvas CSS width/height !important 声明，交由 Chart.js ResizeObserver 管理

frontend/components/dashboard/HistoryChart.tsx

@@ -54,7 +54,7 @@ export function HistoryChart() {
         pointBorderColor: "#fff",
         pointHoverRadius: 7,
         pointRadius: 5,
-        tension: 0.2,
+        tension: 0.1,
       },
       {
         backgroundColor: "transparent",
@@ -65,7 +65,7 @@ export function HistoryChart() {
         label: locale === "en-US" ? "DEB Fusion" : "DEB 融合",
         pointHoverRadius: 6,
         pointRadius: 4,
-        tension: 0.2,
+        tension: 0.1,
       },
     ];
 
@@ -78,7 +78,7 @@ export function HistoryChart() {
         label: locale === "en-US" ? "MGM Official Forecast" : "MGM 官方预报",
         pointHoverRadius: 6,
         pointRadius: 4,
-        tension: 0.2,
+        tension: 0.1,
       });
     }
 
@@ -95,7 +95,7 @@ export function HistoryChart() {
             : `最佳单模型 (${summary.bestModelName})`,
         pointHoverRadius: 6,
         pointRadius: 4,
-        tension: 0.2,
+        tension: 0.1,
       });
     }