优化余量计算，添加预计剩余使用时间。

ExtendWebAITokenChart.js

@@ -27,6 +27,7 @@
 
     let historyByAssignment = {};
     let assignmentNames = {};
+    let currentQuotaByAssignment = {};
     let selectedAssignmentId = '';
     let selectedRange = 'today';
     let myChart = null;
@@ -299,11 +300,20 @@
         refreshAnimationId = requestAnimationFrame(render);
     }
 
+    function getAverageDailyUsage(points) {
+        if (points.length < 2) return 0;
+        const first = points[0];
+        const last = points[points.length - 1];
+        const elapsedDays = (last.timestamp - first.timestamp) / 86400000;
+        return elapsedDays > 0 ? Math.max(0, (last.used - first.used) / elapsedDays) : 0;
+    }
+
     const currentUsageLinePlugin = {
         id: 'currentUsageLine',
         afterDraw(chart) {
             const points = getAssignmentPoints(selectedAssignmentId);
             const currentPoint = points[points.length - 1];
+            const quota = currentQuotaByAssignment[selectedAssignmentId];
             const yScale = chart.scales.yUsed;
             if (!currentPoint || !yScale) return;
 
@@ -311,8 +321,14 @@
             const { left, right, top, bottom } = chart.chartArea;
             if (y < top || y > bottom) return;
 
+            const remaining = numberOrNull(quota?.remaining);
+            const dailyUsage = getAverageDailyUsage(points);
+            const estimatedDays = remaining !== null && dailyUsage > 0 ? Math.ceil(remaining / dailyUsage) : null;
+            const text = remaining === null
+                ? `当前 ${currentPoint.used.toFixed(6)} CNY`
+                : `当前 ${currentPoint.used.toFixed(6)} CNY / 剩余 ${remaining.toFixed(6)} CNY${estimatedDays === null ? '' : ` [预计 ${estimatedDays} 天使用完毕]`}`;
+
             const context = chart.ctx;
-            const text = `当前 ${currentPoint.used.toFixed(5)} CNY`;
             context.save();
             context.setLineDash([7, 5]);
             context.strokeStyle = '#facc15';
@@ -462,6 +478,7 @@
         const used = numberOrNull(quota && quota.used);
         if (!assignmentId || used === null) return false;
         const point = [Date.now(), used];
+        currentQuotaByAssignment[assignmentId] = { remaining: numberOrNull(quota.remaining) };
         historyByAssignment[assignmentId] = historyByAssignment[assignmentId] || { recent: [], archived: [] };
         historyByAssignment[assignmentId].recent.push(point);
         historyByAssignment[assignmentId] = compactPoints([