fix: 调研/产品/UI阶段耗时改为精确时间戳计算

- VersionPlan 新增 actualStartAt 字段
- updatePlan 流转到 in_progress 时自动记录 actualStartAt
- updatePlan 流转到 completed 时自动记录 completedAt（如未设）
- 概览阶段耗时改用 actualStartAt/completedAt 计算（不再用计划排期）
- 个人耗时汇总同步使用实际时间戳

所有阶段（调研/产品/UI/开发/测试）现在统一用精确时间戳算耗时。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/app/versions/[id]/page.tsx

@@ -393,15 +393,24 @@ export default function VersionDetailPage() {
 
                   // 调研阶段
                   const researchPlans = versionPlans.filter((p) => p.type === 'research');
-                  const researchCal = calcCalendar(researchPlans.map((p) => p.startTime), researchPlans.filter((p) => p.status === 'completed').map((p) => p.endTime));
+                  const researchCal = calcCalendar(
+                    researchPlans.filter((p) => p.actualStartAt).map((p) => p.actualStartAt!),
+                    researchPlans.filter((p) => p.completedAt).map((p) => p.completedAt!),
+                  );
 
                   // 产品方案阶段
                   const productPlans = versionPlans.filter((p) => p.type === 'product');
-                  const productCal = calcCalendar(productPlans.map((p) => p.startTime), productPlans.filter((p) => p.status === 'completed').map((p) => p.endTime));
+                  const productCal = calcCalendar(
+                    productPlans.filter((p) => p.actualStartAt).map((p) => p.actualStartAt!),
+                    productPlans.filter((p) => p.completedAt).map((p) => p.completedAt!),
+                  );
 
                   // UI设计阶段
                   const uiPlans = versionPlans.filter((p) => p.type === 'ui');
-                  const uiCal = calcCalendar(uiPlans.map((p) => p.startTime), uiPlans.filter((p) => p.status === 'completed').map((p) => p.endTime));
+                  const uiCal = calcCalendar(
+                    uiPlans.filter((p) => p.actualStartAt).map((p) => p.actualStartAt!),
+                    uiPlans.filter((p) => p.completedAt).map((p) => p.completedAt!),
+                  );
 
                   // 开发阶段
                   const devCal = calcCalendar(
@@ -434,9 +443,8 @@ export default function VersionDetailPage() {
 
                   // 调研/产品/UI 用 startTime→endTime 计算
                   versionPlans.forEach((p) => {
-                    if (!p.owner || !p.startTime) return;
-                    const end = p.status === 'completed' ? p.endTime : undefined;
-                    const hours = calcActualHoursByDates(p.startTime.slice(0, 10), end?.slice(0, 10));
+                    if (!p.owner || !p.actualStartAt) return;
+                    const hours = calcActualHoursByDates(p.actualStartAt, p.completedAt);
                     addHours(p.owner, p.type === 'research' ? 'research' : p.type === 'product' ? 'product' : 'ui', hours);
                   });
                   versionDevTasks.forEach((t) => {