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

lib/redis/index.ts

@@ -105,3 +105,30 @@ export async function getCacheHeatmap(): Promise<string | null> {
 export async function publishEvent(event: object): Promise<void> {
   await redis.publish(CHANNEL_REALTIME, JSON.stringify(event));
 }
+
+// Token Leaderboard Cache
+const TOKEN_LEADERBOARD_DAILY_KEY = "cache:token_leaderboard:daily";
+const TOKEN_LEADERBOARD_TOTAL_KEY = "cache:token_leaderboard:total";
+
+export async function setTokenLeaderboardCache(
+  period: "daily" | "total",
+  date: string,
+  data: string
+): Promise<void> {
+  const key = period === "daily" ? TOKEN_LEADERBOARD_DAILY_KEY : TOKEN_LEADERBOARD_TOTAL_KEY;
+  await redis.set(`${key}:${date}`, data, "EX", 60); // 1 minute cache
+}
+
+export async function getTokenLeaderboardCache(
+  period: "daily" | "total",
+  date: string
+): Promise<string | null> {
+  const key = period === "daily" ? TOKEN_LEADERBOARD_DAILY_KEY : TOKEN_LEADERBOARD_TOTAL_KEY;
+  return redis.get(`${key}:${date}`);
+}
+
+export async function invalidateTokenLeaderboardCache(): Promise<void> {
+  const today = new Date().toISOString().split("T")[0];
+  await redis.del(`${TOKEN_LEADERBOARD_DAILY_KEY}:${today}`);
+  await redis.del(`${TOKEN_LEADERBOARD_TOTAL_KEY}:${today}`);
+}