Add remote-auth token helper (get selfbot token via a link, no devtools)

bot/src/get-token.ts uses discord.js-selfbot-v13 DiscordAuthWebsocket: it
prints the Discord Remote Auth URL (https://discord.com/ra/<code> — the same
thing a login QR encodes). Open it on a phone with the Discord app, approve the
"New login" prompt, and the user token is written to .env as
DISCORD_SELFBOT_TOKEN. Works from a single mobile device (no second screen, no
password, no browser devtools). `bun run token`.

bot/package.json

@@ -7,6 +7,7 @@
   "scripts": {
     "start": "bun run src/index.ts",
     "register": "bun run src/register-commands.ts",
+    "token": "bun run src/get-token.ts",
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {