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/utils.ts

@@ -1,6 +1,37 @@
 import { type ClassValue, clsx } from "clsx";
 import { twMerge } from "tailwind-merge";
+import { NextRequest, NextResponse } from "next/server";
+import { validateApiKey } from "@/lib/auth/api-key";
 
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs));
 }
+
+/**
+ * Get today's date as YYYY-MM-DD string
+ */
+export function getTodayDateString(): string {
+  return new Date().toISOString().split("T")[0];
+}
+
+/**
+ * Authenticate an API request with Bearer token
+ * Returns the claw object if authenticated, or a 401 NextResponse if not
+ */
+export async function authenticateRequest(req: NextRequest) {
+  const authHeader = req.headers.get("authorization");
+  if (!authHeader?.startsWith("Bearer ")) {
+    return NextResponse.json(
+      { error: "Missing or invalid authorization header" },
+      { status: 401 }
+    );
+  }
+
+  const apiKey = authHeader.slice(7);
+  const claw = await validateApiKey(apiKey);
+  if (!claw) {
+    return NextResponse.json({ error: "Invalid API key" }, { status: 401 });
+  }
+
+  return { claw };
+}