feat: replace hardcoded usage limits with dynamic env variables (#180)

- About pages now read DAILY_REQUEST_LIMIT, DAILY_TOKEN_LIMIT, TPM_LIMIT from env
- Removed unused /app/api/config/ route
- Numbers formatted as Xk (e.g., 30k, 10k)

app/api/config/route.ts

@@ -1,15 +0,0 @@
-import { NextResponse } from "next/server"
-
-export async function GET() {
-    const accessCodes =
-        process.env.ACCESS_CODE_LIST?.split(",")
-            .map((code) => code.trim())
-            .filter(Boolean) || []
-
-    return NextResponse.json({
-        accessCodeRequired: accessCodes.length > 0,
-        dailyRequestLimit: parseInt(process.env.DAILY_REQUEST_LIMIT || "0", 10),
-        dailyTokenLimit: parseInt(process.env.DAILY_TOKEN_LIMIT || "0", 10),
-        tpmLimit: parseInt(process.env.TPM_LIMIT || "0", 10),
-    })
-}