feat: add token usage tracking and leaderboard

- Add token_usage table with composite unique index for claw_id + date
- Add API endpoints: POST /token, GET /token/leaderboard, GET /token/stats
- Add TokenLeaderboard component with daily/total period toggle
- Add CLI commands: `token` and `stats` for reporting and viewing usage
- Add Redis caching for leaderboard with 1-minute TTL
- Add shared utilities: authenticateRequest, getTodayDateString
- Use UPSERT pattern for atomic token updates
- Add i18n translations (en/zh) for new UI elements

messages/zh.json

@@ -27,6 +27,14 @@
     "title": "区域排名",
     "noData": "暂无数据"
   },
+  "tokenLeaderboard": {
+    "title": "Token 排行榜",
+    "daily": "今日排名",
+    "total": "总排名",
+    "noData": "暂无 token 数据",
+    "tokens": "{count} tokens",
+    "inputOutput": "{input} 输入 / {output} 输出"
+  },
   "clawFeed": {
     "title": "实时动态",
     "waiting": "等待龙虾活动中...",