chore(backlog): maintain task backlog and add changelog fragments

- Move completed tasks (85, 117, 118, 155) to backlog/completed/
- Delete superseded task files (166 verification, 172 drilldown)
- Add stats dashboard milestone m-1
- Add new tasks (190, 194)
- Update task metadata across remaining backlog items
- Add changelog fragments for stats, mpv args, and subtitle filtering

backlog/tasks/task-181 - Add-background-managed-stats-server-lifecycle-commands.md

@@ -5,13 +5,15 @@ status: Done
 assignee:
   - codex
 created_date: '2026-03-17 15:31'
-updated_date: '2026-03-17 15:55'
+updated_date: '2026-03-18 05:28'
 labels:
   - cli
   - launcher
   - stats
+milestone: m-1
 dependencies: []
 priority: medium
+ordinal: 110500
 ---
 
 ## Description