fix: Issue Manager completed过滤器现在可以显示归档议题

- 添加 loadIssueHistory() 函数从 /api/issues/history 加载归档议题
- 修改 filterIssuesByStatus() 在选择 completed 过滤器时加载历史数据
- 修改 renderIssueView() 合并当前已完成议题和归档议题
- 修改 renderIssueCard() 显示 "Archived" 标签区分归档议题
- 修改 openIssueDetail() 支持从缓存加载归档议题详情
- 添加 .issue-card.archived 和 .issue-archived-badge CSS样式

Fixes: https://github.com/catlog22/Claude-Code-Workflow/issues/76

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ccw/src/templates/dashboard-css/32-issue-manager.css

@@ -128,6 +128,29 @@
   box-shadow: 0 4px 12px hsl(var(--foreground) / 0.08);
 }
 
+/* Archived Issue Card */
+.issue-card.archived {
+  opacity: 0.85;
+  background: hsl(var(--muted) / 0.3);
+}
+
+.issue-card.archived:hover {
+  opacity: 1;
+}
+
+.issue-archived-badge {
+  display: inline-flex;
+  align-items: center;
+  padding: 0.125rem 0.375rem;
+  background: hsl(var(--muted));
+  color: hsl(var(--muted-foreground));
+  font-size: 0.625rem;
+  font-weight: 500;
+  border-radius: 0.25rem;
+  text-transform: uppercase;
+  letter-spacing: 0.025em;
+}
+
 .issue-card-header {
   display: flex;
   align-items: flex-start;