feat(02-03): Worker entry — webhook route + /api/session security gate + deploy plumbing (D-11, D-14, D-16, D-17)

- src/webhook.ts: routes exactly /telegram/webhook (grammY cloudflare-mod
  adapter, constant-time secret-token auth against env.WEBHOOK_SECRET) and
  POST /api/session (validateInitData → 401 category-only rejections →
  mintSession one-time token; single mint path, no extra branch — T-02-01/02/06)
- D-14: the only log statement is '[initdata] rejected: <category>' — no
  payload, ids, or timestamps
- scripts/set-webhook.mjs: setWebhook with secret_token + allowed_updates
  [message], secrets read from gitignored .dev.vars, token never echoed
- bot deploy script chains wrangler deploy + set-webhook; wrangler.jsonc
  gains workers_dev (webhook URL target); KV id stays placeholder for the
  deploy checkpoint
- verified: 27/27 tests, typecheck clean, wrangler deploy --dry-run exit 0

bot/package.json

@@ -6,7 +6,7 @@
     "test": "node test/runner.mjs",
     "typecheck": "tsc --noEmit",
     "dev": "wrangler dev",
-    "deploy": "wrangler deploy",
+    "deploy": "wrangler deploy && node scripts/set-webhook.mjs",
     "commands": "node scripts/register-commands.mjs"
   },
   "dependencies": {