Add RCON client + SendCurrency service (AtomCMS-faithful)

- rcon.ts: Node net.Socket transport speaking AtomCMS's exact protocol (raw
  JSON {"key","data"} over rcon_ip:rcon_port, fire-and-forget) with a bounded
  timeout + backoff retry; typed commands matching RconService EXACTLY
  (sendgift `itemid`, disconnect `username`, no-data => data:null, givepoints
  numeric `type`, forwarduser, setmotto/setrank/alertuser, give*). Injectable
  transport keeps command shapes unit-testable.
- send-currency.ts: mirrors the SendCurrency action — RCON deliver, else DB
  fallback (credits -> users.credits; duckets/diamonds/points -> users_currency
  by type 0/5/101).
- env: RCON_HOST/PORT/TIMEOUT/RETRIES. vitest: SKIP_ENV_VALIDATION for unit tests.

Verified: tsc exit 0, vitest 39/39, next build exit 0. Live TCP test deferred
(needs a running emulator).

vitest.config.ts

@@ -11,5 +11,8 @@ export default defineConfig({
   },
   test: {
     environment: "node",
+    // Modules under test transitively import @/env; skip its strict parse so
+    // unit tests run without a populated .env.
+    env: { SKIP_ENV_VALIDATION: "1" },
   },
 });