feat: add conversation search and usage dashboard

.trellis/tasks/08-03-usage-statistics-dashboard/task.json

@@ -0,0 +1,26 @@
+{
+  "id": "usage-statistics-dashboard",
+  "name": "usage-statistics-dashboard",
+  "title": "使用统计看板",
+  "description": "",
+  "status": "completed",
+  "dev_type": null,
+  "scope": null,
+  "package": null,
+  "priority": "P2",
+  "creator": "shiyue",
+  "assignee": "shiyue",
+  "createdAt": "2026-08-03",
+  "completedAt": "2026-08-03T17:52:38+08:00",
+  "branch": null,
+  "base_branch": "main",
+  "worktree_path": null,
+  "commit": null,
+  "pr_url": null,
+  "subtasks": [],
+  "children": [],
+  "parent": null,
+  "relatedFiles": [],
+  "notes": "",
+  "meta": {}
+}